At first, after having Amsoil Synthetic put in at a premium price, I thought my engine was quieter and my fuel mileage had increased. After two weeks, I have now decided that the truck is much louder and my fuel mileage has actually decreased (not sure why). My oil pressure with Amsoil has increased at both idle and on the highway, so I would have figured that the motor would be more efficient, but I seem to be wrong. I have been running with Rotella up until now. Not sure why I seem to want to fix things that aren't broke. Anyone else having the same issues with the synthetic oil?

Over the last three years and 57K miles I have run several different oils. When warmed up at 75 mph I ran/run exactly 67 PSI. Same 38 PSI at idle. I have never seen any difference in mileage and I keep excellent records. Later! Frank

Well, I've been usung 15w-40 Amsoil since after break-in period, and it runs pretty quiet, I have the little tick from time to time, it's not as noticable since brand new, my fuel economy is pretty good, mainly 20 mpg.


I will say this though, weather it's better, weather it's not from the difference of dino, I guess, it's up to the persons gut feelings, you can ask all you want on here who thinks whats best, you will hear about that these trucks run just as good with regular dino oil, wasting money on justifing synthetic, well my answer to you is that I work with a older gentleman (over 60) and I've seen what he has done with it ever since it's came out. That's why I'm using it.


That's my .02 worth, later.http://www.dieselplace.com/forum/smileys/smiley14.gif

I have run dino and Delvac 1. Dino has slightly higher oil pressure for a short time and drops down to be the same as the Delvac 1 after it's been in a while. Happens pretty quick when towing. I am going to stay with the Delvac, actually now it's Mobil 1 truck/SUV. I won't run Amsoil because it is not API certified and my owners manual says the oil must be API certified. Not very likely that it would ever be an issue. I buy the Mobil 1 for $3.99 a qt. locally and it's actually cheaper too. Not saying Amsoil isn't any good but I still don't understand why they don't get it certified.

Even though I can buy Amsoil at a dealer price I still run dino oil in my dmax. I change oil every 5k miles and have the oil analyzed. It is interesting to note that the engine wasn't totally broken-in until 20k miles. Even if I ran synthetic, I would still change the oil every 5k miles, so don't see the reason to spend more. I use chevron delo 400 and buy it at costco.