Scotty,
I acquired a 1996 GMC Yukon from my father with 193,000 miles on it. He owned it for 70k miles and always filled it with Castrol 5w-30 full synthetic every 5k miles. It has a 5.7 liter Vortex V8 and seems to run pretty well. I found a manual for the car that indicates oil changes should be every 3k miles. Should I start changing oil every 3k or stick with the 5k interval the engine has been getting for the past 10 years?
seems like the 5000 is fine considering nothing bad has happened in the past 10 yrs. up to you though. Also, back in those days that was the standard because it makes sense. I don’t buy into these 10k mi change intervals like I used to. I personally never go past 5k mi even with full synthetic oil. Why push it? It’s more marketing and quicker trips to the dealer for work done. For example, when I crack open my F150s manual, it says lifetime diff fluid, transmission doesn’t need changed till 150k mi thats insane. These manufacturers keep extending these fluid change intervals while using thinner and thinner fluids. It’s more about trying to save .5 miles a gallon rather than actual protection for internal parts.
Why change the interval when it's been doing fine every 5k
Maybe if using conventional oil every 3k makes sense. Full synthetic should be fine with 5k oil change intervals
Stick with the 5000 interval.
When you do your oil and filter changes, make sure to either clean (metal body) or replace your PCV valve.
Full synthetic oil changes are recommended every 1 year/5k miles, whichever comes first.
