Nomad Willy
Guru
BruceK wrote;
"Always thought multigrade oils were made as an improvement on single viscosity oils"
That's the problem. Most everybody views MV oil that way. And in your car they are an improvement but not better in your boat. They actually are inferior if you warm up your boat engine rather slowly.
The reason for MV oils in the first place was to be able to start your car or truck engine in the coldest of weather. With the mild Pacific weather on the west coast there was no problem but in much of the rest of the world sub zero weather WAS a problem. Along came 10W-30 oil. And if you put lots of that stuff called viscosity improver (VI) in oil they could make 10W-40 oil. The VI dosn't directly help lubricate your engine so IMO your better off having the oil in your engine than w the VI. The name of the game is to use only as much VI as you need.
I run multi-vis oils in my cars and trucks because often I more or less need it to drive them fairly fast just after startup. I run full synthetic in my new turbocharged car and the 10W-30 that I use probably dosn't have any VI in it as the synthetic oil has the properties of multi-vis oil without any VI at all in the oil. This is because the synthetic oil is more viscosity stable than the dino oils made from crude oil. They don't make 5W-60 oil .. probably because it would require too much VI to make it conform to the 5W-60 specification. So it appears that with that much VI in the oil even the manufacturers of oil think it would not be safe to put on the market. All the manufacturers would love to be the first to offer a 5W-60 oil as it would be viewed as an "improvement" and probably sell quite well. Also you will only find 5W-50 in synthetic oil as it would require too much VI for dino oil. Most people start their cars and drive them normally (or close to normally) when cold so even though they can start their car w straight Wt oil the MV oil is better when they drive their car stone cold on the road. So for cars BruceK the multi-vis is an improvement. Big diesel truck engines warm up slowly and most use MV oil to get the trucks on the road quickly as time is money in the business.
BUT .. with our boats we don't "drive" them right away. We warm them up before operating them fairly fast and under load. So we do not need the MV oil. And straight weight oil has more oil in it and as a result better lubricity. MV oil in your car is a useful feature but serves no purpose in your boat.
"Always thought multigrade oils were made as an improvement on single viscosity oils"
That's the problem. Most everybody views MV oil that way. And in your car they are an improvement but not better in your boat. They actually are inferior if you warm up your boat engine rather slowly.
The reason for MV oils in the first place was to be able to start your car or truck engine in the coldest of weather. With the mild Pacific weather on the west coast there was no problem but in much of the rest of the world sub zero weather WAS a problem. Along came 10W-30 oil. And if you put lots of that stuff called viscosity improver (VI) in oil they could make 10W-40 oil. The VI dosn't directly help lubricate your engine so IMO your better off having the oil in your engine than w the VI. The name of the game is to use only as much VI as you need.
I run multi-vis oils in my cars and trucks because often I more or less need it to drive them fairly fast just after startup. I run full synthetic in my new turbocharged car and the 10W-30 that I use probably dosn't have any VI in it as the synthetic oil has the properties of multi-vis oil without any VI at all in the oil. This is because the synthetic oil is more viscosity stable than the dino oils made from crude oil. They don't make 5W-60 oil .. probably because it would require too much VI to make it conform to the 5W-60 specification. So it appears that with that much VI in the oil even the manufacturers of oil think it would not be safe to put on the market. All the manufacturers would love to be the first to offer a 5W-60 oil as it would be viewed as an "improvement" and probably sell quite well. Also you will only find 5W-50 in synthetic oil as it would require too much VI for dino oil. Most people start their cars and drive them normally (or close to normally) when cold so even though they can start their car w straight Wt oil the MV oil is better when they drive their car stone cold on the road. So for cars BruceK the multi-vis is an improvement. Big diesel truck engines warm up slowly and most use MV oil to get the trucks on the road quickly as time is money in the business.
BUT .. with our boats we don't "drive" them right away. We warm them up before operating them fairly fast and under load. So we do not need the MV oil. And straight weight oil has more oil in it and as a result better lubricity. MV oil in your car is a useful feature but serves no purpose in your boat.
