What viscosity?

[wtd]

I have two 98 Chevy trucks. One is a K1500 Z71 with the 5.7L and the other is a K3500 with the 7.4L. 5.7L has 105,000 miles on it and the 7.4L has about 98,000 miles on it. I have been told I should move up to a 10w30 for the 5.7L and 10W-40 for the 7.4L. Both trucks use a little oil but don't smoke. Both have some startup tapping that goes away when warm. I've had the K1500 since new and the K3500 for about a year.

GM recommendation for both engines is 5w30 but with the higher mileage it was suggested that both engines would be better with a higher viscosity.

So, what do you guys think? Stay with the 5w30 or move up. I don't want any synthetic recommendations. I went that route years ago with the 5.7L and wasn't satisfied with the results. Thanks for any input.

Wayne

 

[rg200amp]

I would stay with a 5w30, what the car maker recommends.

You may want to try a quality High Mileage oil like Maxlife.

 

[WishIhadatruck]

I'd stick with the 5w30. I've used 5w30 in GM engines to 200k miles and beyond with no issues.

 

[addyguy]

Valvoline MaxLife 5w30 or 10w30 FTW!

 

[TallPaul]

I'd run 10w30 in both.

 

[labman]

Where are you buying you oil? If I lived that far south I might go with the 10w30 that Wal-Mart is selling their Pennzoil Conventional for about 60% of the 5w30. With the winter temperatures here, I coughed up the $15 for a 5 qt bottle and another 6 for the ST 9018 cartridge filter my car takes.

 

[wtd]

I buy my oil at Walmart and I have been using 5w30 Havoline in both vehicles. Thanks for the input. Keep it coming.

Wayne

 

[Ken2]

10W-30 and 5w30 are will be very close in viscosity at normal operating temperature. I'd stick with the 5w30 in the winter for sure for better cold lubrication. In the summer, I don't think it will make any difference.

The engine only needs thicker oil if the bearing clearances have worn appreciably. If you think this is the case...if the oil pressure is lower than it should be at normal warm highway speeds, for example, go to a 10w-40 in the summer. Otherwise stick with a 30.

Has the oil usage been consistent over the time you've owned the trucks? If so, you probably don't have a problem. You might have good results cleaning the engines internally with Auto-Rx. It does a very successful job of cleaning the ring grooves and oil control rings to significantly reduce oil consumption, as well as cleaning sludge, carbon, and varnish from the engine. It is also very effective in transmissions and power steering. I've used it with very good results.

 

[daman]

High mileage? my '99 5.7 has 226,000+ and see's 5w30 summer 0w30
winter and blows 40psi oil pressure,100k is nothing on these
motors,,stick with the recommended 5w30 for both trucks..

thos engines with that mileage would not be better with higher viscosity,why?

 

[wtd]

Originally Posted By: Ken2
10W-30 and 5w30 are will be very close in viscosity at normal operating temperature. I'd stick with the 5w30 in the winter for sure for better cold lubrication. In the summer, I don't think it will make any difference.

The engine only needs thicker oil if the bearing clearances have worn appreciably. If you think this is the case...if the oil pressure is lower than it should be at normal warm highway speeds, for example, go to a 10w-40 in the summer. Otherwise stick with a 30.

Has the oil usage been consistent over the time you've owned the trucks? If so, you probably don't have a problem. You might have good results cleaning the engines internally with Auto-Rx. It does a very successful job of cleaning the ring grooves and oil control rings to significantly reduce oil consumption, as well as cleaning sludge, carbon, and varnish from the engine. It is also very effective in transmissions and power steering. I've used it with very good results.


Thanks for the replies. On the 5.7L, when it was new it didn't use any oil that I remember and the oil pressure was higher. Now it uses probably a quart in 3,000 miles and runs about 50psi oil pressure running down the road and about 25psi at a hot idle in gear. The 7.4L uses about the same amount of oil and has about the same oil pressures.

I've changed the oil on the 5.7L every 3,000 miles since new except one intervel of 5,000 miles. The 7.4L I have only had for a year and I've changed it once after the initial oil change which was a new change when I bought it. I don't know the oil change history for this engine but the oil stays fairly clean and the engine doesn't have any weird noises after it warms up.

I've used AutoRx in the 5.7L as well as LC & FP. I've used some LC & FP in the 7.4L but no AutoRX.

Wayne