Thanks for your replies guys.

I want to start using Quaker State Full-Syntec for diesel trucks and suv's, in 15W40. A friend of mine changed to this oil in his 617 and got a compression increase of 10-15 psi per cylinder.

Switching to thisoil was kind of easy for him, because he was raplacing his cooler and hoses, aswell as the pan gasket and some engine seals.

He also noticed a reduction in oil consumption and engine blow by. Usually he had to pour a quarter in the engine between oil changes (3000 miles interval) and now there no significant oil consumption, maybe 1/4 of a quarter.

Could all this be true? I can't swear over this, this is something I didn't verified myself. He was using Pennzoil Longlife 15W40

Thanks!

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1982 W123 300D NA Euro, 300K Miles, 4-speed manual, 3.46 rear diff, early W126 front brakes, Penta rims with 205/60R15 FH900's, custom fitted (by me) audio system, more to come into the money pit... Soon to be installed: Bilstein HD, R107 front discs and 4-piston calipers, HD Suspension springs, wagon front swaybar.