I only run the 5w40 synthetic now. I had an issue with my old Mercedes not wanting to crank for me in -20*F weather. New battery did not solve the problem. Switched from 15w40 Rotella to 5w40 Rotella synthetic and she cranked over with enough rpms to start, no problem in the same weather.

I was sold, and have kept it in all my diesels since. It's a little more expensive, but it ensures easier cold cranking.

Now that it is mentioned... I do notice at least a stinkier blow by in the dually. Blow by is minimal in the utility truck

 

I use 15w40 in my truck from Amsoil. They have a membership program which drops the cost of one oil change enough to pay for the membership.

Since ordering I've also switched to Amsoil in my wife's Equinox...and on the last road trip I took in it, we managed to average 26 MPG, which was better than the last best of 23 MPG. I don't know if the oil is the only credible source of the increased mileage, but it seemed to help.

 

ya Ams oil is pretty cool we have a chevy cavalier with almost 500,000 on the odometer and she is still ticking like new proving the worth of synthetics

 

I run Amsoil full synthetic 15w40 in my truck along with their filter and boy its good stuff. I've put over 2,000 miles on it so far and the oil isn't even completely black yet, just a very dark brown. I noticed, my oil pressure comes up much quicker when i start it especially in the cold and also my engine coolant ran much cooler, it would stay right under the first line. I'm also a preferred customer and run it in our snowmobiles and am gonna be switchin the rest of my truck over to it.

 

Have any you guys expereince oil seepage when you went from dino oil to synthetic?? Heard that vehicles that have ran dino oil all their lives will start to leak oil when converted to synthetic oil...

 

I've never experienced that, but I've heard about it before. Not sure if it's an old wives tale or not. I guess it stands to reason that it could seep a bit more, but if you tried it and it was too messy, you could always switch back on the next oil change. I KNOW it's an old wives tale about not being able to switch back and forth.

 

ya I got ams oil for my rig but she might be parked for a while now cause of ball joints and a brake problem and I just dont have a lot of cash right now

 

I've heard of it but didn't experience it. I ran rotella t 15w-40 before I switched to the series 3000 5w-30 synthetic amsoil and it didn't seem to seep any more than it did before. Possibly even less.

 

I've heard of it but think it's been sensationalized a lot. I switched my 96 to synthetic when I bought it 6 years ago with 190,000 km on it, and still haven't had a leak or even any seepage. I think it may seep past any seals that are already marginal, but I don't believe it actually causes any problems that weren't already lurking.

 

thats pretty darned good

 

Haven't noticed anything out of the ordinary..... But I haven't looked that hard either. It's cold enough these days that there is always plenty of smoke from my beast.... My rear main seal doesn't think much the synthetic but that didn't really surprise me....

 

Ok thank you sir. Knock on wood but the single cab has no real leaks to speak of. I've jusr noticed more blowby with the t6, so was wondering if this is something others are experiencing as well. It's not going to stop me from running it. I'm tracking my fuel mileage as well and seems I'm up a hair, but weather is cooler now too so not a very accurate statement yet.