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Old 10-10-2019, 07:23 PM   #21
Lou_tribal's Avatar
City: Quebec
Vessel Name: Bleuvet
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Originally Posted by Rufus View Post
Our boat has become pretty much a dock condo in recent years. I had been leaving the dino oil in the crank case over one winter. Last Spring I switched to Rotellla T6 synthetic because I believe it is the perfect solution for extended "down" periods. Judging from the look of the oil after one season, I might go for two winter storage periods (I'll do an oil analysis before launch this Spring. If I'm comfortable with two storage seasons...I'm making money over dino oil. Further, I swear the engines are running more cleanly with the synthetic. I'm sold on the stuff. $4 a gallon difference...please. T-6 is going in my E-type Jaguar at the next change.

Not sure I understand what is expected from synthetic vs regular oil if the boat is in storage and the engine not ran??? Oil sits in the pan so what’s the difference?


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Old 10-10-2019, 08:52 PM   #22
City: Great Lakes
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Some of the literature says the synthetic produces and retains less of the potentially damaging pollutants than dino. It sure looks it when I look at the dip stick.

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Old 10-11-2019, 12:40 AM   #23
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City: Lake Stevens, WA via Honolulu
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Originally Posted by catalinajack View Post
A quick googly and I found both Walmart and a local Advance Auto Parts selling T6 for $20.
I can confirm about the same price in the store (Walmart); $20 and change/gallon. I just bought 4 gallons of T6, 5W-40 for my F-250. 15W-40 is the same.
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Old 10-13-2019, 11:42 AM   #24
City: NC
Join Date: Jan 2014
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I have been using synthetics for decades in my truck, which has an International engine, and my JD tractor, which has a Yanmar engine.

The truck oil is supposed to be changed every 5,000 miles. I change at 15,000ish. Friday I changed at 16,000ish. I get a UOA done and last years test said to try 17,000 miles but the weather was nice and I had time to get some chores done so the oil got changed "early." UOA over the decades has said I have been throwing away good oil even with the high miles/hours on the oil. The worst the oil has even been was during a time where I was getting stuck in bad stop and go traffic. Fuel was in the oil from the extending idling BUT it was still within spec.

Why do I use synthetics? It saves me time and money. I get slightly better MPG, when it gets cold I don't have to hook up an engine block heater which really drives up my power bill even using a timer, and I only change the oil and filter once a year instead of three times.

With UOA I know how the engine is wearing.

Is it worth it on a boat?

If you use JD synthetic in a JD engine, you can increase the oil change hours to up to 500 hours instead of say 250. That might be worth it for some and not for others.

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Old 10-13-2019, 01:16 PM   #25
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City: Concrete Washington State
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 18,115
It may not be a question of “is synthetic oil good in old engines” but what is it about synthetic oil that is questionable?

With that in mind if an additive was a problem one would have problems w some syn oil and not other brands.
Also syn oil comes in a fairly wide variety of base stocks. So if there’s a problem it may be due to a specific base stock.

What caused big problems in the 50’s was much higher levels of detergents. An old car nearing the end of it’s life with the newer high detergent oil very often had a big problem w sludge deposited over many years loosened up by detergents. “Gaps” that were filled w old sludge would become gaps and rods would rattle and where sludge was performing the job of oil seals the engine would leak large amounts of oil. These engines would self destruct rather quickly.
Some people thought it was the MV (multi-vis) element of the new oils that caused the problems.

Oil leaking problems were a big problem when syn oil first came out significantly but this was caused be the tendency for syn oil to shrink oil seals. Correct me if I’m wrong but I believe they put an additive in the oil that swelled oil seals. And if they put in the ideal amount the seals stabilized and the leaking problems stopped. But if they fluck up and put the wrong additive in or the wrong amount the seals could shrink up. It could happen but I don’t know if it ever does.

Anyway the problems of switching to syn in an old engine could result from additives and it could have nothing to do w the syn base stock.

All my life I’ve heard mechanics say not to change the kind of oil you use in any engine. Long before syn oils came out. And syn oils came out via the US Army needing to start equipment like trucks and tanks in very cold weather. Our boat engines never get below 40 degrees or so and hence have no clold weather problems at all. I spent 8 (or so) years in Alaska, used Chevron DELO 30wt oil (and still do) and never had even a hint of slower cranking when starting.

As I’ve said before syn oil has some advantages but I consider those advantages to be fly stuff. Also I can walk up in any SE Alaskan town and get more new oil.


North Western Washington State USA
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