I use sythetic oil. I think many, perhaps even most, members here do. I don't have a bypass filter setup, yet, so I use fairly short intervals, about 5,000 miles between changes. I should do analysis to determine whether I should adjust those, but I haven't gotten around to it.
I have a dual remote bypass and run to 7500 ish. I have run to 7800 and pulled early as 6700. It all depends on what's going on and the mood I'm in. I think you could use the GM life monitor if you run synthetic, but I would only go to 5K with dino. That is only an opinion with no scientific proof, testing or other data. A good method to set life time is oil analysis. I have been taking mine just before a change to develop a baseline. Of course, being an enginerd
I will take whatever data I can. I prefer synthetic for any catastrophic failures. I had a car that didn't blow an engine because I used synthetic. To me the extra money is like insurance, agian IMO.
I run Delvac 1 with changes at 7,000. When I get my Racor by pass filter (same as oil gaurd) installed I will be going to 10,000 miles. I have my oil checked each change by AV Lube to make sure that all is well!
I'm using the Rotella Syn myself. I change every 5000-6000 miles. The only real way to go to extended drain intervals is by constant analysis. There are way to many variables to just go by a set number.
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