4.1L L6 OHV Oil Question

[rustyoldjunk]

Hello,

I have a 1981 GMC High Sierra with the 4.1L L6 OHV engine. I just changed the oil and put Castrol GTX 10w40 conventional with around 800-900 ppm for zinc. I'm just learning about zinc in oil and flat tappet engines, and was wondering whether the conventional 10w40 was fine or if I'm getting neurotic over another over-hyped piece of internet lore.

Thanks,

 

[CleanSump]

1.Yes
2.Yes

 

[novadude]

Those engines have very mild camshafts and low valve spring loads. I think Castrol GTX 10W-40 will be just fine.

 

[nascarnation]

I run Pennzoil Platinum 5W30 in my 67 Chevy 250 six. Although it won't accumulate enough miles to be a good test case. The cylinders were significantly worn before I rebuilt it but the cam and lifters looked like new.

 

[JavierH19]

It'll be fine for 3k or a year. If it was mine I'd use 15w-40 next time.

 

[GI_GRIFF]

Hello,

I have a 1981 GMC High Sierra with the 4.1L L6 OHV engine. I just changed the oil and put Castrol GTX 10w40 conventional with around 800-900 ppm for zinc. I'm just learning about zinc in oil and flat tappet engines, and was wondering whether the conventional 10w40 was fine or if I'm getting neurotic over another over-hyped piece of internet lore.

Thanks,

I would possibly go with Shell Rotella T4 15W-40. That oil is actually a diesel oil, but I have known many friends here where I am from that have used it year-round here in our absolute four seasons of Nebraska in their gas engine pick-up trucks with great success. They use it in their cars, trucks and diesel farm equipment and their lawn mowers also. I have never used it myself. The Rotella T4 has a zinc level up around 1200 PPM. The temperatures here run from 110 F to -20 F actual temperatures, not wind chill or heat index calculations. In the winter most usually have an engine block heater plugged in when sitting outside overnight, however. Here is a link to the Rotella web page.

https://rotella.shell.com/en_us/products/triple-protection-motor-oil/rotella-triple-protection.html

 

[Vexorg]

Hello,

I have a 1981 GMC High Sierra with the 4.1L L6 OHV engine. I just changed the oil and put Castrol GTX 10w40 conventional with around 800-900 ppm for zinc. I'm just learning about zinc in oil and flat tappet engines, and was wondering whether the conventional 10w40 was fine or if I'm getting neurotic over another over-hyped piece of internet lore.

Thanks,

That is a low power, low RPM truck engine. 10w40 will be fine in that engine. If you have any questions on it's past history then Valvoline Restore and Protect is the new superstar oil. 5w30 would suit that engine just fine as well.

 

[CleanSump]

Just because newer formulations don't have the high levels of zinc doesn't mean they don't do a better job than the old low tech oils of 60s-80s. Quite the opposite. And HDEO is not a panacea for motors. Leave hotrod folklore with old Uncle Bob and his shadetree.

 

[rustyoldjunk]

Thank you for the replies. Maybe I will do 5w30 in the winter and 15w40 in the summer next time too .

 

[The_Jeff]

Is this a daily driver or just on weekends?

 

[ka9mnx]

Thank you for the replies. Maybe I will do 5w30 in the winter and 15w40 in the summer next time too .

5w-30 would be fine year round.

 

[CleanSump]

As @ka9mnx wrote and you will find in many threads here, there is no need to change oils for Summer/Winter. The engine won't care if you use a 5W in Summer and it also won't get any magic from HDEO 15W-40.
0W-30, 5W-30, 0W-40, and 5W-40 are all good for year round use. Just pick one and stop worrying about hearsay and myths.