vettet80

so my 99 frc rolled over to 250,000 miles today just before my diy oil change early this morning. changing the oil was fairly straight forward. the new oil i put in was mobile 1 synthetic 5w-30. i used a mobil 1 oil filter as well.

so since i changed the oil, i been noticing there are now a lot of new oil spots when ive been parking in the garage. so i take the car to run some errands for a while and parked the car outside for a couple hours. there were fresh oil droplets marks on the driveway within 3-4 hours after i parked it. i checked underneath the car and it looks like there is a thin film of oil on the bottom of the oil pan batwing. i wiped it up with a clean rag and checked again a few hours later. i just jacked up the car a bit higher this time and it looks like it is coming from the block area. i thought i saw some oil on the left exhaust. maybe this is sometimes why ive noticed the smell some burning oil at times after i did do some spirited runs even before the oil change.

so could this be as simple as an oil pan leak or is it coming from the block somewhere? im kind of getting frustrated now. i didnt expect this problem from such a nice car. anyone here ever encounter this kind of oil leak problem before? somethings telling me the oil pan gasket is bad. if it is a bad oil pan gasket, how long of a job is this? is this a fairly easy 4 hour diy job or a couple of days?

lucky131969

Don't be too hard on the car....250K is pretty generous without an oil leak..

Best bet is to degrease(not power wash) the oily areas, get underneath, and see if you can determine the origin. Nothing wrong with double checking your work....tightness of the drain plug/oil filter.

vettet80

drain plug, check.

oil filter, check.

i really didnt see any leaks until right after this oil change. could it be that 5w-30 synthetic is too thin for the mileage? should i have gone with a thicker synthetic oil like 10w-30?

clydeyb

My Vette has 112,000 miles and experienced the same situation after an oil change and have the same question. Is there a common area it might leak from? Is it a big job to change oil pan gasket? any other place it might leak from? My leak is very minor but would like to take care of it. This is my plan for this weekend, to investigate. I had a '93 Vette with 80,000 miles and had the same thing happen after an oil change but it stopped. I believe the shop I had the oil changed at during state inspection might have slightly over filled it. Could you have slightly overfilled it?

ipuig

Do not assume that a 10W-30 oil is thicker that a 5W-30, it's a common misconception. The low temperature viscosity number (10W, 5W) only applies for the sub zero temperatures it's tested for.
If you read Mobils's product data sheets, you will find that the Mobil 10W-30 has a slightly lower viscosity at operating temperature (100 deg C) than the 5W-30 formulation. They are both 30 weight oils so both fall within the SAE's viscosity range for a 30W oils.

clydeyb

The way it was once explained to me was (don't know this to be a fact) that 5-30w oil would be slightly thinner than 10-30w beause in order to obtain the weight ranges the 5-30w on average would have to be slightly thinner oil?

But anyway, does anyone have any suggestions or answers to the original post?

bobby777

Very few cars see 250,000 miles--likely alot of wear on many different parts-drive it and let it drip

pear

Just a thought here... Don't discount the posibility that the filter may be leaking, even if you checked it for tightness. When you removed the old one did the gasket from it come off with the filter? They can leave the old rubber gasket from time to time causing leakage when the new one is installed. Also before you applied the new filter did you lube the new gasket? (a little oil swiped around with the finger works great or just a dab of grease) Applying a dry gasket can allow it to drag and bunch up allowing for a poor seal. The latter is the more common problem but both are very posible. My feeling is that if it wasn't leaking before the change, you will find one of these to be the case. Keep us posted. ..."pear"

wcsinx

A quarter million miles, and you "didnt expect this" little oil dribble? Show me a car with all original seals at that mileage that isn't leaking something!

Wipe everything off as best you can and keep looking for it. Oil will "creep" everywhere, so it can be hard to tell where exactly it's coming from. If in doubt, you can get a vial of UV dye (sold at any parts store) which you dump in the crankcase. Then you shine a blacklight around, and the leak shows up clear as day.

vettet80

i just put in some uv dye awhile ago and drove around ran errands as usual. ill check it in a few hours. hope this problem isnt too bad...

wcsinx

You're probably looking at a pan gasket. It's not a hard job... just messy and tedious. Definitely double check the oil filter before you pull the pan though. I've seen several times people double stack the gaskets because the old one stuck to the pan, and they didn't realize it.

dgrant3830

I'm the one with the super high mileage '99 that I gave away to my son. I saw too a leak developing which I wasn't sure of where. Took it to the dealer and they found the oil pan was starting to leak and apparently there is a plug for a distributor hole even though we don't use one and its seal was leaking up high on the rear of the engine. No more leaks. Also, never, never allow it to just leak because of the miles or any other reason. Oil is flammable and the result isn't pretty. A dude here in the apartment complex where I live had a '91 (I think), went up in flames due to an oil leak and I have the pictures if you wish to see them.

clydeyb

Thanks for the post! My leak seems to be from the passenger side rear of motor of the car when standing in front facing the car. Do you know off hand if that's where that that plug might be? Also basaar as it may sound, it seems worst with the climate control off?

TEXHAWK0

If it only leaked a couple of drops of oil, we already know it is not too bad.
I find that when I run mine all the way at the full mark, or above, then I get a small leak where the top oil pan butts up against the rear cover plate. Running the oil level a little lower reduces the leak.
I think the back corner relies on sealant, and not a gasket, getting into that corner when the engine is assembled.

dgrant3830

On mine, that's where the oil was showing up. Its really hard to see where this plug was as its on the backside of the motor but apparently the dealers know about it. You might just have the pan starting to leak too.

vettet80

the oil filter gasket is intact. no leaks there. looks like the uv dye indicates i have a leak on the oil pan batwing and possibly the oil pan-to-block gasket. ah..... this sucks. means im not gonna be driving this until i fix it. i dont want the car to burn down while im driving. at least i gotta spare car. its gonna be a long week or two.

dgrant3830

This is what happens when a leak isn't fixed...happened in my complex where I live

padojada

Im glad i did mine. it was leaking bad from the oil sending unit.

vettet80

ummmmm....... ouch!!!! btw is he selling the wheels?

Bill Dearborn

That had to be a lot of oil. I have seen many, many oil leaks on engines over the years that were ignored and nothing happened. The old style mouse and rat motors almost always had oil leaks. Chevy's used to be known for wet bottoms. With rear oil seal, pan gasket, intake manifold and valve cover leaks there was no way to keep them dry for long. My 86 leaked down the back of the engine on the passenger side for the 10 years I owned it. Replacing valve covers and the intake manifold gasket did not stop the leak. Every time I parked the car it would leave a puddle of oil about 3 inches across. Finally, I just put a pan on the garage floor and stopped worrying about it.

Bill