How to find oil leaks so I can use synthetic oil?

[gustavohuber]

So I know this is a pretty contentious issue.. but all I'm asking is how I can find out if I have leaks that would make running synthetic oils a bad move. I'm kinda seduced by the longevity of them... 15k guaranteed on Mobil 1.. I have 5w30 dino/standard in my crankcase, and factory goo in my diff currently, and its just about due for an oil change....

also, if synthetic oil is really a rip-off, tell me why. We have oodles of the stuff at work, but if dino is really better for my car, I'll go buy some.
/Gus

[legacy92ej22t]

The whole point isn't really that your existing leaks make it bad to run synthetic (they will still leak and perhaps a bit worse) but that when you switch to synthetic, you can strip the build up off your seals that aren't leaking, creating leaks where there wasn't any before.

[gustavohuber]

right, and there's no reasonable way to check for nacent leaks. and i'm guessing that without the buildup, no amount of seal sweller would keep the oil at home. so.. synth is something you either have to do to a young vehicle, or not at all. which begs the question young in mileage or young in years? my wagon has only seen 63000 miles in 12 years, which suggests that it saw a lot of sitting around before I got it.. think it will have leaks? not worth finding out?

[professor]

In my experience the biggest benefit of synthetic is that it doesn't thicken up so much when it gets cold, so the engine starts more easily cold, and the valvetrain gets oil faster on a cold start.

I have personally seen and tested synthetic to see how much better it is when cold, and how much more difficult it is to burn it when it gets too hot.

In your case the cold start issue is not so large since you may see 40 regularly but not -10F.

Yes it is true that you may develop some leaking if you switch, but it is my opinion that this is exaggerated and you may well not have any leaks. Further, the seals tend to expand with the use of mineral-based oils (the elastomers swell), since there are things running around in them that are not straight alkane chains, whether deliberately added or just part of the witches brew that is mineral-based oil. Synthetics being, well, synthetic, there is not as much of that high solvent strength "stuff", so seals may not stay swelled and leaks could develop on older cars in particular.

In the winter on older cars I have personally used a mix of one quart mineral "old car oil", stuff that has extra additives to keep seals tight, and 3 quarts synthetic. That gives me easy cold starts and I've never had leaks suddenly develop. In the summer I tend to use the mineral on older cars.

Do not buy into that 15,000 mile garbage, if you have a little blowby or sludge in a car, it matters not how long the oil theoretically lasts, but how fast it becomes tainted. For me 5,000 miles strikes a good balance between the oil-change-company induced 3,000 mile zeolotry, and the spurious claims of longevity beyond reason.

[gustavohuber]

Thanks. The eventual home for this car is at home in the olympic peninsula, where thick oil might be more of a concern.. but for posterity, i'll keep it dino.

[tris91ricer]

The eventual home for this car is at home in the olympic peninsula

So you're comin' up here?

[gustavohuber]

Yeah. Port Townsend is home, but I've been down here thumping pavement with a heavy vehicle simulator for UC Berkeley and Caltrans.