Sojo300E

i have a 91 300E with a little over 119k miles that i recently switched to synthetic oil. I've heard both positive and negative experiences with switching to synthetic with an older engine.

so the problem is.. I'm losing a lot of oil, i just put in 4 quarts last week... and the dipstick reads nearly empty now. there definitely is something wrong. I don't see oil drips on the floor, but i do smell burning oil in the morning. When i park my car i see really thin white smoke come from under my car.

Whats going on with my car?

Mansoor 300

Dont use synthetic oil !

Since the velocity of the oil is much thinner, it can leak much easier through the gaskets.
I am pretty sure that's your problem, especially with your engine at this age/miles.

Sojo300E

yeah, the next chance i get im going to switch it back to conventional.. should i go for 15-w50? i live in orange county in southern California.

CDP

Where do you live in Socal?

Anyways, on the M103 engine I wouldn't run synthetic oil in there. Apparently you're leaking a lot of oil.

Have you change the valve seals? Those are typically changed during the miles you have on your car right now. Those are the first symptoms of increased oil use. Also, The M103 is notorious for having leaks at the head gasket, front timing cover and the valve cover gaskets. You might want to have those checked out. Another thing to check out is your oil pan. Make sure there isn't a crack or even a hairline crack in there. Trust me - I have experience with this.

On my E420 right now I have a hairline crack the size of 2 inches in my oil pan (thank god it's getting fixed). Everytime I would drive my car hard the oil would spray on to the downpipes of my exhaust and cause white smoke to appear.

Also, when I use to have my 300E I usually ran 20W-50. Good Luck! I have a really good mechanic in Orange if you're interested. A few of the local W124 owners have gone to him with good turn outs.

RogerJones

My M103 Twin Turbo has been run on fully synthetic for all of its life from new, in accordance with the strict instructions from Turbo Technics. When I bought it, there was a slight leak, but any oil would have got through that classic fail-point at the corner of the head. Gasket fixed; no leaks since.

The M103 in my W126 was switched to Mobil 1 thousands of miles ago and does not leak or consume more oil than it did on semi-synth.

Perhaps the white smoke is significant. I'd get that checked out first. From the Web:

"White smoke is due to water getting in to a cylinder from a bad gasket, cracked block or a cracked head."

YNVDIZW124

The white/blueish smoke could be a leak at the valve cover gasket when the oil leaks onto the exhaust manifold. I wouldn't use synthetic because the rubber gaskets on these cars get hard and leak. I currently run 10w-40 Mobil clean high mileage with good results and i even have a front timing cover leak.

jmoney6

do you get any performance usuing synthetic, because i was considerign switching.

Sojo300E

i felt a slight performance increase.. or maybe my mind just wanted to justify switching.. haha. currently im in Irvine for school but i usually come home on the weekends to Hawthorne (near Torrance).

Isn't the head gasket repair about 2k? whats the damage estimate if i have to replace the seals?

shdoug

Where do you live? Sojo? Isn't that a warm place? I think about the only benefit of synthetic oil in an engine designed for conventional is the wider range of temperatures that it can be used in. So if you live in Nebraska you can use the same oil in the summer that you do when you start your car and it's -20 outside.

I would never use synthetic oil in an engine that is not designed for it. My '95 E320 used conventional MB oil from the day it was built and with 162,000 miles on it the rockers and camshaft looked like brand new and it never leaked or burned a drop. You can't convince me that synthetic oil is better than petroleum based oil unless you're in Siberia or Phoenix.