question on going from conventional oil to synthetic on smaller engines

[daugen]

I know that mixing moly and lithium greases isn't a good idea, but mixing oils was always a concern, but I've never read where anyone
had a major problem. Has anyone here put full synthetic in an older engine and had a problem? Seals? Gaskets? Oil consumption?

I had forty year old 8V71TI's in my boat and those old Detroits spec'd 40 weight. But now Grumpy has me wondering, 40 or 40W?
I always, mistakenly..., thought the W mean weight, not winter.
I'd go to the store and there would be the jugs of T4, T5, and T6.
I used T4.
Today I might try T5 in an older engine.

if the only difference between an air cooled engine and a liquid cooled one is the temps they run, and if they have hot spots,
really any good oil should work.

do small air cooled engines need any special additive pack?

used to be you stuck with the heavier oil since you didn't want it to "break down".
Now I think they don't break down so easily any more.

 

[Williy]

When I lived in Wisconsin 10W30 synthetic oil was all I ever used
and never had any problems with the cars/trucks that burned gas
also used the same in the small engines with no problems.
Believe it or not I have a briggs & stratton engine that I put 10W30
synthetic oil in and never changed it and its still running from 1987

willy

 

[Grumpycat]

I'll say it again, "synthetic is not a motor oil performance specification".

And mention B&S currently sells engines "which never need an oil change". Advertises as such, just top it off. Sticker on side of the engine says so. Wiser minds note this is a self-fulfilling prophesy. "Don't change the oil, just change the engine!" Plenty of YouTube videos pouring sludge out of these B&S engines which have been "maintained" per B&S instructions.

 

[SylvainG]

When I lived in Wisconsin 10W30 synthetic oil was all I ever used
and never had any problems with the cars/trucks that burned gas
also used the same in the small engines with no problems.
Believe it or not I have a briggs & stratton engine that I put 10W30
synthetic oil in and never changed it and its still running from 1987

willy

My 1991 B&S land mower has only seen W30 conventional oil and still starts on the first pull. Had to change the carburetor film and primer bulb, but that's it. Oil is changed yearly in the spring before its first seasonal use. I do start it for about 5 minutes to warm up the oil before the oil change. I also always run it until dry and pour about an once of fresh oil in the sparkplug hole before storing it for the winter.

 

[John0829]

Whether it is conventional or synthetic the lubricating properties degrade with use. Mostly due to contaminates.

 

[aircommuter]

I know that mixing moly and lithium greases isn't a good idea, but mixing oils was always a concern, but I've never read where anyone
had a major problem. Has anyone here put full synthetic in an older engine and had a problem? Seals? Gaskets? Oil consumption?

I had forty year old 8V71TI's in my boat and those old Detroits spec'd 40 weight. But now Grumpy has me wondering, 40 or 40W?
I always, mistakenly..., thought the W mean weight, not winter.
I'd go to the store and there would be the jugs of T4, T5, and T6.
I used T4.
Today I might try T5 in an older engine.

if the only difference between an air cooled engine and a liquid cooled one is the temps they run, and if they have hot spots,
really any good oil should work.

do small air cooled engines need any special additive pack?

used to be you stuck with the heavier oil since you didn't want it to "break down".
Now I think they don't break down so easily any more.

Yes to changing to full synthetic having problems. I had been using Mobil one as my synthetic in various vehicles for several years. Then Castrol came out with theirs. So I tried it in my Mercedes V12. Within a week I had oil leaks from static O rings. I replaced the O rings and put the Mobil 1 in it. I think that Castrol did not have the additives need to keep the rubber expanded. The car only had 35k on it, now over 80k and no leaks.

 

[5030]

Whether it is conventional or synthetic the lubricating properties degrade with use. Mostly due to contaminates.

...and depletion of the additive package due to the heat and cool cycles, which is why it's hard on any combustion engine to not run it at operating temperatures, for at least a while or do some expressway driving. The around town stuff destroys an engine faster because it allows moisture to build up in lube oil and in the fuel tank as well

 

[Grumpycat]

It wont hurt to do that but its been taught forever not to go from synthetic to conventional oil

Old Wive's Tale.

Once Upon A Time it was "well known fact" one should not change brands of motor oil once the engine was started until a full rebuild. "Oil seals leak" was the justification. And it was mostly true, manufacturers didn't design for oil seal swelling. One brand would swell the oil seal, then another not so much so the worn swollen seal would shrink and leak.

Then along came synthetic motor oil. Once again the knowledge of motor oil technology didn't include oil seal swelling characteristics so synthetics didn't swell at all. Fine if new engine run it's entire life, seal worked fine. But a swollen refined oil seal shrank when bathed in the synthetic motor oils of the day. Leaked. "Don't change from refined to synthetic!"

Today every respectable motor oil certification agency includes similar oil seal swelling characteristics so all oils swell seals similarly and are safe to freely change from one to the other.

 

[aircommuter]

Back in the seventies we changed our entire fleet of over 100 cars and trucks to Mobile 1 and we didn’t have any seal leakage. Which tells me they had the oil additive package very well worked out.