Hi, I read some advice on another thread about using synthetic 20W50 oil in a high mileage motor that had developed a knock. My 1998 had a leaking intake gasket which I fixed but it has since started knocking. I did change the oil several times right after the repair to get as much water out as possible. (I replaced the gasket a few weeks ago and it seemed fine until yesterday when it started knocked pretty bad.)

I believe Mobil 1 20W50 synthetic was the recommended oil. The only oil I have been able to find like that is designed for motorcycles. Is this the oil that was being recommended? The blazer is very clean and I bought it recently so I am really hoping to get some more miles out of it. Thanks

 

tough call. try running 10w40 first maybe. i used that in my mazda b2200 and the ticking basically quit entirely.

 

Your 98 was designed to use 5W30 oil. Using higher viscosity oil will increase oil pressure, which might quiet it down temporarily, but at the same time, oil volume will decrease and cause more damage. If the engine knocks using 5W30, the damage is done.

 

Yeah, I figured as much but I am hoping to keep it going for my girlfriend until I get home to deal with it. (I am working out of town for the next month or so) Can the pan be dropped without removing the engine to change the crank and bearings or would it be easier to just yank the motor and have it rebuilt? Thanks for your input.

 

Best to pull it out, check it all out, and do it right.

 

If it is knocking it is best to pull it and redo the whole thing. Even if you have a new crank there could still be metal shavings and oil/water mixture throughout the engine. Or you can do what I did and get a junk yard motor with a 6 month warranty.

 

no mobile one no longer makes a synthetic 20 W50 for high mileage vehicles. Iran, the castrol gtx, synthetic 20 W 50 in mine.

 

just don't use 20w50 in anything including race cars - it's obsolete.