Oil heat vs coolant heat

I've read a lot of various posts about warming up oil or coolant using various systems.

What I haven't been able to determine are the pros/cons of each approach. Both seem to help with cold starts in differing ways, and both can provide warmth in colder months, as well as reduce condensation, etc.

I'm considering a system like this for my dual 1988 Volvo TAMD 61A engines which tend to be a bit on the smokey side when starting, and take a long while to warm up.

Most people have said a coolant heater would be most appropriate for my engines given that it takes forever for them to warm up, and the smoke would be reduced with this approach. Given what I know about the engines, I think that a coolant heater is most likely the right approach, but they are also quite expensive, require some plumbing changes that could be risky depending on how they're done, etc. Side benefit - I could plumb my water heater into the thing so I could have hot water all the time (which I do not have now).

Oil heaters are far cheaper and seem easier-ish to install, although getting to the underside of my oil pan is going to be an exercise in lots of bendy routines/scraped arms. They could help with warming up, but more on the oil and lubrication side if I understand the application.

I'd love to hear from people in terms of what they saw before/after with each system and thoughts on pros/cons of each one.

The ideal solution (if possible) is to heat both. Heat the oil pan so the oil is warm and ready to flow easily on startup. This doesn't require a ton of heating power in most cases, particularly in a boat where there's no wind blowing past the engines. Heat the coolant (with more power) to get the rest of the engine warmer so the cylinders, etc. are warm at startup for better combustion, getting out of the high-wear cold start phase faster, etc.

Having the cylinders warm with a coolant heater will help, if not solve the smoke issue. Warm oil will benefit startup lubrication, but won't do as much for the engine block unless left on continuously. Some block heaters can be installed where there is a soft plug, so no plumbing, easy to do except for draining some coolant.

We ran coolant heaters on a pair of 6-71 Detroit's. They did a great job at reducing smoke at start up.

Lepke said:

Having the cylinders warm with a coolant heater will help, if not solve the smoke issue. Warm oil will benefit startup lubrication, but won't do as much for the engine block unless left on continuously. Some block heaters can be installed where there is a soft plug, so no plumbing, easy to do except for draining some coolant.

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That's what my engineer brain was telling me, even though a particular mechanic disagreed.

I hadn't thought about a soft plug or other way to plumb something like this in. I was looking a long while ago for an in/out set of plugs so I could plumb the coolant into my hot water tank loop to keep that warm underway, but never found one. I didn't look that hard, though, and I bet it could be in my Volvo manual.

If you're engine(s) are closed cooled and you have an engine oil cooler, I would think that a coolant style heater would work to heat the oil as well.

ben2go said:

If you're engine(s) are closed cooled and you have an engine oil cooler, I would think that a coolant style heater would work to heat the oil as well.

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Depends on if the coolant heater leads to any meaningful circulation. Some of the plumbed-in ones will, a freeze plug heater less so. And even with closed cooling, some engines still use raw water for the oil cooler.

rslifkin said:

Depends on if the coolant heater leads to any meaningful circulation. Some of the plumbed-in ones will, a freeze plug heater less so. And even with closed cooling, some engines still use raw water for the oil cooler.

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True.

Does Volvo not make a block heater for those engines? Most diesels have provisions for one, and two pieces of construction equipment that I have (non-volvo) came with them as standard equipment. That said, I've never used them and am thankful the engines start right up even in sub-zero F conditions.

My knowledge of engines pretty much ends with knowing how to start and stop them. FWIW, I put an oil pan heater on my Cummins 5.9L engine a couple years ago. I didn't have any starting or smoking problems but just wanted to keep the engine warm enough to keep it dry in the wet months. I put a 250W heater on the oil pan and it keeps the engine block temps in the 50's even during sub-freezing weather. It also keeps the rest of the ER from getting too cold.


If you heat the oil pan, heat rises. This keeps the whole engine a lot warmer. I leave the heater on 24/7. Has worked out great. On a really cold day, it does help to bring the engine coolant temps up more quickly, but most of the time it makes little difference.

I went the block heater route. Put a factory one in my 4045 JD. I left for Florida several years ago in February. Water temp in the Chesapeake was about 34 degrees and so was the engine room. Plugged the heater in 8 hours before leaving. Engine was around 75 when I started it. Don't know what the oil temp was but I'm sure it got some benefit as the engine room was in the 40s.

Ted

twistedtree said:

Does Volvo not make a block heater for those engines? Most diesels have provisions for one, and two pieces of construction equipment that I have (non-volvo) came with them as standard equipment. That said, I've never used them and am thankful the engines start right up even in sub-zero F conditions.

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I'm not sure if they ever did. Maybe for non Penta versions that were used in trucks and such in Europe.

There is a pre-heater coil on these engines that you can use for cold weather starts, and that nearly caused a fire on my boat due to a bad key about a year ago (scroll down past the gratuitous food pics).

It is designed for cold weather starts and helping initial combustion.

I know that Tony Athens prefers the Wolverine oil pan heaters. Maybe because he sells them but more likely because heated oil circulates better and reduces crankshaft resistance while cranking.


David

dhays said:

My knowledge of engines pretty much ends with knowing how to start and stop them. FWIW, I put an oil pan heater on my Cummins 5.9L engine a couple years ago. I didn't have any starting or smoking problems but just wanted to keep the engine warm enough to keep it dry in the wet months. I put a 250W heater on the oil pan and it keeps the engine block temps in the 50's even during sub-freezing weather. It also keeps the rest of the ER from getting too cold.


If you heat the oil pan, heat rises. This keeps the whole engine a lot warmer. I leave the heater on 24/7. Has worked out great. On a really cold day, it does help to bring the engine coolant temps up more quickly, but most of the time it makes little difference.

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I saw your posts from your install. I do like the idea of keeping things warm, although I use pipe insulation halves to block the engine intakes in cold weather, and a small 500W heater in the engine room, which keeps things warm. The oil pan heater would definitely provide even more warmth.

However, I'd need 2x of the 500W model as I have 5.1 gallons of oil per engine, dual engines, and the 250W one is too small. That's quite a bit of power (1000W) to be constantly sucking from the dock just for the engine room!

O C Diver said:

I went the block heater route. Put a factory one in my 4045 JD. I left for Florida several years ago in February. Water temp in the Chesapeake was about 34 degrees and so was the engine room. Plugged the heater in 8 hours before leaving. Engine was around 75 when I started it. Don't know what the oil temp was but I'm sure it got some benefit as the engine room was in the 40s.

Ted

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Sounds like a perfect setup!

stevemitchell said:

However, I'd need 2x of the 500W model as I have 5.1 gallons of oil per engine, dual engines, and the 250W one is too small. That's quite a bit of power (1000W) to be constantly sucking from the dock just for the engine room!

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My engine has 3.5 gallons of oil per engine, so smaller than yours. However, if it is something that you keep on 24/7 while at the dock, the heat will radiate through the engine quite nicely. That would be too little wattage if you were looking to warm up the engine before starting, but is plenty to keep the engine from getting too cold. Also, two engines in the ER, each with a 250W oil pan heater will be more effective than one engine with a 250W oil pan heater. Same reason two folks stay warmer cuddled together under the covers in bed.

You can run a smaller than recommended pan heater as long as you accept the long heat-up time. Plus, sizing recommendations for those are often based on cars / trucks with more airflow through the engine compartment to suck away heat. And if you run an oil pan heater and a block heater, then the pan heater definitely doesn't have to be huge.

dhays said:

My engine has 3.5 gallons of oil per engine, so smaller than yours. However, if it is something that you keep on 24/7 while at the dock, the heat will radiate through the engine quite nicely. That would be too little wattage if you were looking to warm up the engine before starting, but is plenty to keep the engine from getting too cold. Also, two engines in the ER, each with a 250W oil pan heater will be more effective than one engine with a 250W oil pan heater. Same reason two folks stay warmer cuddled together under the covers in bed.

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I only wish my engines cuddled more together, but that's another post for another time.... And I would definitely have them on quite a while before.

rslifkin said:

You can run a smaller than recommended pan heater as long as you accept the long heat-up time. Plus, sizing recommendations for those are often based on cars / trucks with more airflow through the engine compartment to suck away heat. And if you run an oil pan heater and a block heater, then the pan heater definitely doesn't have to be huge.

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Fair point though on an open air engine vs one inside my engine room. And I would definitely have them plugged in quite a while before starting, or potentially all the time in the winter.

Also very true on the combo of both. I'd like to start with one first, for sure, and the more I read and based on responses here, I think the smoke issue I'm trying to make better would be best solved with a coolant heater.

"I'm considering a system like this for my dual 1988 Volvo TAMD 61A engines which tend to be a bit on the smokey side when starting, and take a long while to warm up."

A block heater helps with cold starts , if the engine is hard to get firing in below freezing weather.
For DD below 40F can sometimes be difficult on older engines.

Smoke from incomplete combustion is simply the sign of a cool engine.

The best, fastest and correct way to warm the engine is to get underway at a very modest engine load , and increase the load as the engine warms.

30 seconds to 60 seconds is all the idle time needed before casting off

WE run about 1,000 RPM till the water temps get to about 120F then increase throttle to continue the warm up.

Steve, I put a 250w oil pan heater on my 5.9 liter Cummins several years ago and I like it better than the block heater that preceded it (and failed).

The oil pan heater uses a lot less power (the block heater was 1500w IIRC.), so I leave it on all winter. The big block heater seemed large to leave running 24/7, and it simply wasn’t practical to leave running on a 30 amp connection while living aboard the boat (although you might solve that with automated load shedding or a modern inverter that’s can supplement the 30 amp shore power). I also feel better about leaving the boat unattended with a lower draw ER heater.

With the oil pan heater running 24/7, the engine starts instantly with very little smoke at all temperatures we experience in the PNW. Without the oil heater, starting is noticeably smokier and slower, especially with a cold soaked engine room in winter.

Retriever said:

Steve, I put a 250w oil pan heater on my 5.9 liter Cummins several years ago and I like it better than the block heater that preceded it (and failed).

The oil pan heater uses a lot less power (the block heater was 1500w IIRC.), so I leave it on all winter. The big block heater seemed large to leave running 24/7, and it simply wasn’t practical to leave running on a 30 amp connection while living aboard the boat (although you might solve that with automated load shedding or a modern inverter that’s can supplement the 30 amp shore power). I also feel better about leaving the boat unattended with a lower draw ER heater.

With the oil pan heater running 24/7, the engine starts instantly with very little smoke at all temperatures we experience in the PNW. Without the oil heater, starting is noticeably smokier and slower, especially with a cold soaked engine room in winter.

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Thanks Sam! The coolant heater will likely help more, but it is a much bigger install and huge cost in my case.

I think I will try a couple of 250W oil pan heaters to start, as they would replace the 500W air heater I leave in the room anyhow.

I don't live aboard technically, but I am on the boat almost every day, and with 30 amps as well, having more than that would be problematic, even with the fancy Victron system I have now.

If you don't want or need to leave the heaters on all the time, Thermocube turns on at 35°F and off at 45°. Rated for 15 amps, under $20 on eBay. Cubes come in other temp ranges, for turning on AC, etc. I use them to turn on my Detroit engine block heaters in cold weather. If I leave them on (1500 watts each) the engineroom is 70° in a few hours in zero weather. Having them on the Cubes keeps the engineroom about 40° and protects the generators and plumbing. Although since I live aboard, I've never measured below 34° in zero weather w/o heat in the engineroom.

The hassle with the 250w magnetic oil pan heaters is long term the constant heat in one spot burns the oil into carbon chunks.

Most converted coach owners will use them in an emergency , but install in block coolant heaters for long term good winter starting.

FF said:

The hassle with the 250w magnetic oil pan heaters is long term the constant heat in one spot burns the oil into carbon chunks.

Most converted coach owners will use them in an emergency , but install in block coolant heaters for long term good winter starting.

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Depends on the pad size and how well the heat gets distributed into the oil. If any spot on the oil pan inner surface is getting too hot, this can definitely happen. Synthetic oil will survive a higher temperature before this happens.

That's part of why I'm a fan of coolant heaters, but using a smaller oil pan heater so the oil isn't stone cold at startup (having both coolant and oil pre-warmed means you can load the engine up more right after startup).

Lepke said:

If you don't want or need to leave the heaters on all the time, Thermocube turns on at 35°F and off at 45°. Rated for 15 amps, under $20 on eBay. Cubes come in other temp ranges, for turning on AC, etc. I use them to turn on my Detroit engine block heaters in cold weather. If I leave them on (1500 watts each) the engineroom is 70° in a few hours in zero weather. Having them on the Cubes keeps the engineroom about 40° and protects the generators and plumbing. Although since I live aboard, I've never measured below 34° in zero weather w/o heat in the engineroom.

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You mean this? I have a funny story about mine.... It was in the engine room plugged in when I bought the boat, and a few weeks after, I needed to plug something in down there.

I was scratching my head trying to figure out why the AC outlet wasn't working, flipping breakers, and eventually just unplugged what I thought was an odd thing to have in the engine room - a splitter on an outlet that likely does not get much use.

It wasn't until a couple months afterwards that I realized it was a temp controlled Thermo Cube

I think I'd want one with a slightly higher temp level for my setup. But I have one

Steve,
I have a automatic block heaters on Kubota Tractor. Makes all the difference in the winter. I plan on putting them on my Internationals before I splash next summer for the trip north.

ThermoCube comes in several temp ranges. And there are plugin devices that let you set your own range. Some have remotes. About $25 on Amazon

I bought a Wolverine from Seaboard Marine. Couldn't be easier, glue it to the side of the oil pan. After a while even the top of the engine is slightly warm to the touch. It's heat exchanger cooled so oil is warm and coolant is warm.

Lepke said:

ThermoCube comes in several temp ranges. And there are plugin devices that let you set your own range. Some have remotes. About $25 on Amazon

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Yup, I've seen the other temp level ones. I've also used some IoT stuff from SmartThings and other companies to automate some of my heaters on the boat before. The ThermoCube is a lot simpler and more reliable than those though, although the IoT stuff you can at least check on remotely to see how they're doing.

sean9c said:

I bought a Wolverine from Seaboard Marine. Couldn't be easier, glue it to the side of the oil pan. After a while even the top of the engine is slightly warm to the touch. It's heat exchanger cooled so oil is warm and coolant is warm.

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I'm definitely going to go the oil cooler route first for the time being and see how things go.

The coolant heaters keep the block warmer so it is easier for the fuel to self ignite in really cold weather. Winter starting is their main purpose .

Lube oil pumps are geared so oil is pumped regardless of its viscosity. Only a pressure pre lube system might reduce engine wear during the first few seconds of cold starting.

Following the eng. mfg. ("Da Book") for out of service storage is the best way to winterize engines.

Usually a far different more complex procedure than sticking a magnet on the oil pan.

Back when my father was a Deutz tractor dealer, in 1977, we had a huge snow-storm (Huge by Georgia's standards) and we went out, knocked the tractors in neutral, pulled out the starter button to start the glow plugs warm-up, then cranked them up. This was about 5 degrees F and they didn't seem to care it was cold, as long as the glow plugs warmed up first.