I have a 115 mile commute everyday in my 04 Trailblazer with a 4.2 and 140,000 miles. I routinely change the oil at 5000. I've always used name brand conventional oil. Would there be any advantage switching to synthetic?
You could possibly change the oil @ a higher mileage interval?
Instead of 5000 miles, 6000?
What type of oil does GM say to use? Syn or conven?
Supposedly less wear on engine internals? More HP, less friction?
Downside, cost more $$$
MBHD
The only reason I was even thinking about it, was that the local home improvement store has Quaker State synthetic on sale. It's only slightly more expensive than the conventional right now. I was thinking it may help squeeze a little more fuel economy out, since I'm driving so far. It may be so insignificant that it's not worthwhile.
I couldn't discern any measurable MPG difference when I switched.
For a DD, I'd probably just use regular dino oil and change it when the manual/DIC says.
5000 miles on todays oil ???????? in my engines oil is worn out at 2500 miles. I wouldnt even consider going any longer. 5k is in synthetic oil teritory and I suggest nothing but amsoil
X2-
I have always wanted to and finally did an oil analysis. There is no way of knowing exactly the condition of your oil without one. I drive a 7.3L powerstroke DD and I interval the change at 5000 miles. I use Mobil Delvac 1300 and they recommended I extended to 7500 miles. The traditional OCI is just a recommendation.
I do not drive my Inline 250 turbo enough to actually analyze it. I just change it once a year.
If you have not been to the site, Bob Is The Oil Guy, google it and get ready to be informed.
Boucher'
I go 7500 miles or more with both my 6.0 Powerstroke's with synthetic. One of them has almost 250,000 miles on it and the oil still looks clear and light brown even then unless I do a lot of heavy towing.
OC every 5000 miles since the day I bought it. That was over 120,000 miles ago. I believe the book recomends every 7000 for highway driving and 3000 for severe duty. I checked the oil the other day, It still looks just about like it did when I put it in. Not black at all, heck it is about 4000 mile into the oil change now.
Chris
I have heard that changing over a higher milage motor to synthetic oil would "invent" leaks.