Just turned 100k - should I change oils?

I just turned 100k on my '97 c2500. I had been considering trading it for a similar, slightly newer, lower mileage, k2500. I'm also considering keeping it. It does what I need, and I suppose I don't really need a 4x4 although it would be nice here in the winter months (NJ).

Anyhow, now that I'm over 100k miles I'm considering switching to either a high mileage or synthetic oil. I'm concerned that changing may cause oil leaks (or is that a myth?), but I also want to treat the engine right. What do folks here recommend?

Thanks!

Personally, I would not switch to synthetic now at this time with 100K on the clock. You don't list what you are running but I would probably stay with what you are running.

Synthetic will not cause oil leaks but it will find them.

//2000CAYukon

With 100k on my '98 Sub K2500 7.4 I switched from Castrol GTX 5-30 to Castrol High Mileage 5-30 and it drank like water?? Went back to the GTX and consumption is back to normal (1 qt every 2500 miles).

Great, thanks for the info. I've been running dino 5w-30 as recommended (which surprised me when I took notice). I probably go through a half quart every 3000 miles, give or take. I was thinking about the HiMi oil, or maybe a synthetic blend, but I think I'll stick with what I'm using. I'd read through the other past threads on this in the forum and there didn't seem to be a real resolution - to each their own I suppose!

I've put many V8s past 100k then past 200k, never changed the oil type. Personally I don't consider 100k 'high mileage'. Some engines begin to use oil, others don't. It mostly depends on how they've been treated but not always. In the past, old timers always said to never change the type of oil you were using in an engine. There often turns out to be alot of truth in what old engine builders say.

I've put many V8s past 100k then past 200k, never changed the oil type. Personally I don't consider 100k 'high mileage'. Some engines begin to use oil, others don't. It mostly depends on how they've been treated but not always. In the past, old timers always said to never change the type of oil you were using in an engine. There often turns out to be alot of truth in what old engine builders say.

Sounds good. I've heard a lot of "car rules" myself over the years. The problem is with all of the changes in today's vehicles you are never sure which ones still apply. You end up wondering stuff like should I use synthetics? Should I trust anything lighter than 10w40? Should I believe them when they tell me to change the trans fluid or do I leave it alone? What may have been safe 30 or more years ago may be detrimental today!

I think I'll stick with the dino 5w30.

Sounds good. I've heard a lot of "car rules" myself over the years. The problem is with all of the changes in today's vehicles you are never sure which ones still apply. You end up wondering stuff like should I use synthetics? Should I trust anything lighter than 10w40? Should I believe them when they tell me to change the trans fluid or do I leave it alone? What may have been safe 30 or more years ago may be detrimental today!

I think I'll stick with the dino 5w30.


The only way what was safe 30 years ago is detrimental today is if today's engines' internal workings are more fragile than before. Three generations in my family have run only 30HD in everything (southeastern US) and never have a serious internal problem that would be lubricant related, except for a few engines that were really abused. Bottom line, pick something and stay with it. The majority of what you see out there is just advertising, plain and simple.

The only reason I would change oil types is if there's been a change in usage or performance. I have 190K on my 94 and have run QS 4X4 Semi-synthetic since day 1. I have no signs of blow-by or excessive usage. I change about every 3-5K miles and it uses about 1/2 to 1 quart in that time.

Synthetic will not cause oil leaks but it will find them.

//2000CAYukon
That is a great way to put it!