My 1991 420SEL (112,000 miles) consumes about 1 to 1.5 qts of oil per thousand miles. Is this normal? I'm keeping up with it, and have the oil changed every 3,000 mi. like all my cars. Use only Pennzoil or Castrol SAE 10W30 year round (no synthetic).

Great performance otherwise as far as I can tell. Several years ago, while my Mom owned it, the car sat in her garage for a year without being driven at all (in Los Angeles -- mild temperatures year-round). Could the period of non-use have been detrimental?

Thanks!

Bob
Charlotte, NC

Bob-

A similar post recently said that a quart per 1,000 was generally acceptable even with new cars. To me that doesn't seem right, but hey, who am I to argue with the guys who built them. Personally, I get ansy if I'm having to add any oil between a 3,000 mile oil change.

my 560 was consuming WAY too much oil (quart per 200 miles) and I'm putting the finishing touches on it right now (have another thread going with my trouble getting it to file up). The prior owner used Pennzoil 10-30 and it did a good job of sludging up the engine (not just walking away from dyno in general, Pennzoil in particular, I'm running!). Top end rebuild at 70,000 miles is way premature.

Do you have a puff of black smoke when you first start the car, but dissipates quickly? Typically when the car has been sitting for a few hours?

In the older cars MB considered a quart in about 600 miles acceptable. In those days, sometimes you just ended up with a car that used oil. The luck of the draw.

In the latest generation engines, from most all manufacturers, they just don't use ANY oil. It's almost scary.

Anyway you're about at the acceptable limit, so I would just keep a close eye on it and be happy.

You might do a search on valve seals for these engines. It could be that they were plagued with the same valve seal problem as the M103 engines. Sorry I can't help with that part, but I have no intimate knowledge of the V8's.

Merry Christmas and good luck with it,

10w-30 really isn't the proper weight to use. But it sounds like your valve seals could be getting hard. I had teh same problem with my Camry I used Castrol High Mileage for 10k miles and blue smoke on start up and consumption went down. They also offer it in 10w-40 and 20w-50.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

On a 1991 model with only 112K-miles, I'll assume the car either sits for some periods or undertakes short duration trips. This can lead to some problems with seals hardening, including valve seals. They get brittle with age, but in my own experience, it's worse on cars with low mileage for their age.

Larry right about new engines being scary. In 170,000kms (106K-miles) my C230 has not used one drop between changes. It's freaky to a guy that has had nothing but M102 and M103 engines that used "something" nearly their whole lives.

__________________
John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Thanks for all your replies.

Question: How much $$ am I looking at (parts/labor) to replace the valve seals ?

Thanks again!!

Bob