Switch of viscosity

[sleepery]

I have a 1978 Chevy van with a 292 . I began using 20w50(recommended by previous owner) then went to 10w40 because I could not find the 20w50 any more . No real difference. Last year I used 10w30 Pennzoil and then 10w40 Pennzoil high mileage(was on sale 9 dollars for 5 qts) .

I topped off with about 2 quarts of 5w30 over the last oci and the motor is pretty quiet compared to a few years ago . Probably a 30% difference. It still has a ticking noise after warming up .

I still get a few oil drops under the van after a drive of 20 minutes or more. I was wondering if going down to a 5w30 for my next oil change is too much of a change for an old motor .

 

[Steve S]

What is the oil pressure hot and how much more oil does the engine burn.

 

[sleepery]

I have noticed that I need to top off the oil more now than a few years ago . This was the first oci that I used 2 quarts to top off . I think it leaked the most with sustained speeds of 50-60mph over 20-30 minutes . I use the van for painting, mostly around town but sometimes do a job where I drive on the highway to get there . When I do this it really leaks . If I drive around town I can go a month or so without adding oil . I feel it is ballpark 75%oil leak 25% burning oil .
I do not have a guage for the oil pressure but would be interested in finding out what it is .

 

[FL_Rob]

how many miles? just curious.What about a conventional 10w40 high mileage?

 

[Frank D]

I think 10w30 was the recommended grade in 78. I know it was in 76. I think you should use either a regular 10w30 or a high mileage 10w30. If it uses a lot of oil, try 10w40 high mileage.

 

[StevieC]

Older engines like that are susceptible to fuel dilution from the richer running engines. I would run a 10w40. Also because the engine has much wider clearance tolerances.

 

[Merkava_4]

I'd be tempted to run 20W-50 Valvoline in that engine of yours, and I'm basing that opinion off of the 1978 Cadillac that I used to own. It had a 425c.i. V8 and it absolutely loved 20W-50. It ran so quiet, that all you could hear is the fan belts rolling over the pulleys. As previously mentioned, the clearances in an engine play a big part in selecting a viscosity; the looser the engine is, the thicker you're gonna want to go.

 

[Doug Hillary]

Hi,
Frank D - You are correct 10w30 was the oil then. That is what I would use today - a good quality "run of the mill" 10w30 mineral oil

 

[HTSS_TR]

I would try high mileage 10w30 for a couple OCI's.

 

[jorton]

Originally Posted By: sleepery

I do not have a guage for the oil pressure but would be interested in finding out what it is .


Good idea. Base viscosity selection on oil pressure instead of leaks.