How much is too much

[Pomorza]

Hey guys.

About three months ago I did an oil change and poured in some 10w-30 VR1 into my 280z. Two weeks ago I noticed the oil pressure is a bit low for my liking. (it sat about halfway up at acceleration, usually it sits just under 3/4). Anyhow I pulled the dipstick and to my dismay it was VERY low. Went to the local NAPA and bought two quarts. Poured on in one and was on me way. (oil registered great).

Today I checked the oil once again and it was again getting to the L on the dipstick. I've driven about 300-350 miles since the last fill up. I have don't have any white/blue or any other colored smoke coming from the exhaust. The exhaust doesn't smell like oil at all. What could be up? I know the oil pan is leaking moderately but 1 quart for 350 miles? Could the oil just be too thin and be getting through other areas.

Thanks

Jan

[Curtis240Z]

what about oil sheen in your radiator water?

[Pomorza]

None. Radiator fluid looks, smells and tastes normal;). There's no oil in the radiator and no rad fluid in the oil. I checked this past weekend as its part of my inspection. I check all fluids every Saturday morning.

Jan

[IdahoKidd]

Pull the plugs and have a look. It is either leaking out (oil slick or all over bottom of car) or it is burning it up. I have heard of slick 50 being sucked past the rings so it could be doing the same.

[DeesZ]

Curious, what weight oil were you using prior to the change to 10W-30?

Back in the '70s, I switched from 20W-50 GTX to 10W-30. The car consumed mass quantities (and blue smoke was visible upon hard acceleration / deceleration). Back to the 20W-50, and there was no problem at all.

Just a thought for consideration -

[d240zx2]

I've been told by my Z guru, Doug Bakke of Awesome Z here in Houston, that the L series engines needed the 20w50 oil. He went into a 10 minute dissertation about why and I was convinced. Don't expect me to even TRY to remember what he said. I just pour in Royal Purple 20W50 and drive on.

[Walter Moore]

Since he is in Arizona the 20W50 might be acceptable. In Indiana using oil that heavy in any month other than July or August is suicidal.

I have been running 0w40 in mine since the rebuild with no oil consumption. But then what passes for a cold day in TX or AZ most of the year would be considered normal here.

[ajmcforester]

Missing oil and you say, you don't see smoke or oil in the coolant. Then it is leaking on the street, but if it was than much you would have large puddles under the car. MY bet is you are burning out when you step on it and you just can't see it in the mirrors. Has anyone you know drive behind you while you put her under a load?

Also do a compression test and leak-down test you need to see if your seals are good worn piston rings can cause a lot of damage. These cars are old a lot can go wrong. If you used a heavier weight and no leaks, but when you went to the lighter weight you might need to rebuild the engine the tolerances are not up to snuff any more.

My 4/71 engine has never been rebuilt no leaks, at a 120,000 On top of that, I run 5w-30 with no oil loss. I had a Ford Ranger that I drove for 240,000 mile when the engine was getting warren and started to louse oil I used a heavier weight before the rebuild it can delay the enviable, but if you do this check your compression and do leak downs regularly. to see if the piston-rings are still good. I made it to 40w60 before the rebuild when the head cracked (common problem with the 2.9L V6 with cast iron heads). Heavier oil is a band-aid it only hides the problem for a while.

[Pomorza]

Thanks guys for the idea. Idahokid. I did a tune up about three weeks ago. All plugs looked good and showed no sign of oil burning but I'll look at em again. DeesZ before this I used 10w-40 but as its been fairly cold here (30's in the morning) I switched to a lower weight. I'm really timid about using 20w50 oil. To me it seems to thick. Has anyone have any problems with using such a thick oil. Note there is a fairly descent amount of oil on the underside of the car.

Thanks guys

Jan

[IdahoKidd]

I'm betting the thinner oil is getting past a seal and you are loosing more of it than you might think. Plus, if you changed oil types at the last tune up, the new problem may now be showing up on the plugs. Pull one just to see if there is anything out of line.

[DeesZ]

I'm not recommending 20W-50. I do not use it in my 240 these days. You may wish to go back to the weight you were using previously to see if your problem backs off.

[Pomorza]

I'm betting the thinner oil is getting past a seal and you are loosing more of it than you might think. Plus, if you changed oil types at the last tune up, the new problem may now be showing up on the plugs. Pull one just to see if there is anything out of line.

I actually didn't do an oil change at the tune up. Just did plugs and air gap. The oil change was done well before. I'm thinking the thinner oil is getting past the oil pan gasket or something. The driver's side of the engine about a foot or two in has a fairly large amount of sludge sitting on it. I'm going to take a lot of a closer look at it this weekend.

ajmcforester you are more than likely right that I'm burning some of it on heavy acceleration. I can see smoke coming out upon heavy acceleration in second. I thought due to its gray/black appearance that it was carbon build up. IT could possibly be oil burning. Guys the car has 240k+ on it from all the investigation I've done on it. So it doesn't really amaze me that there is some oil loss.

Jan

Edited February 23, 2010 by Pomorza