5W30 or 10W30, synthetic or traditional? Opinions wanted

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88sclb350

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I’ve just heard so many things from different folks, read things on this forum and Reddit but I just want to raise the question again.

I have an 88 k1500 350 with 150k on it. I’m not a great mechanic but to me it is about as good as you’d expect an engine to be in a 30+ year old truck with 150k miles on it. So not pristine and not clapped out.

My FIL who’s a mechanic for 30 years says to absolutely use traditional non synthetic oil. He says to use 5w30 as well but a lot of guys tell me in an older truck to be running a heavier oil like 1020 or 1030.

I just wanted to raise the question again of what you guys put in your higher mileage more work type GMT400s and why.
 

Drunkcanuk

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Definitely don't use synthetic unless you wanna find every place oil can possibly leak out of these motors.
As for viscosity, thinner if it's colder, thicker if you are in a warm climate.
 

Caman96

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FWIW, I’ve been using synthetic oil on my 96 and the only place I see anything is a “slight” weep on bolts for oil filter adapter, which is common for these trucks.
 

Jeepwalker

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I've literally used Citgo dino oil from our local Farm & Barn since I got my license (35 some yrs ago) in everything I've owned. It's the least expensive oil the local Farm & Barn sells ..but it's name brand.

I keep my vehicles a long time ...and have driven all my vehicles to 200k to 300k miles. Never had an engine fail, ever. Or become an oil burner either. My vehicles usually rust out and I replace them. LOL. Oil change interval is typically around 5000 miles. I usually use the OEM filter (Mopar in Chrysler, Delco in GMs), or a Wix filter. My '89 OBS truck has 270k miles and runs great. I use the same Citgo dino oil in that and always have. I used to change it about every 5K, but these days it's not my DD so I change it more frequently.

The exception is my Jetta TDI. I've used Shell Rotella T6 synthetic in that (oil change interval 10k - 12k miles (you read that right)). It's also got about 275k miles on it and runs great.

I use 10-30 in the summer, 5W-30 in the winter (gets cold up here)

.
 
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Drunkcanuk

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I’m not following you brother
I think what they are alluding too is this question has as many answers as those who answer it. Everyone has different opinions on oil. I would default to the original OE spec oil, as this is what the lawyers and engineering agreed upon to be comfortable offering a warranty.
 
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