Anyone see a difference in milage or anything by running synthetic, I have always ran delo 15/40 in all my diesels and never had any problems. Change my oil every 3000- 5000 miles. Synthetic is also double the price is it really worth it.

 

it depends. where do you live??? does it get really cold outside?- how often do you want to change your oil?. delo is a good oil- if you are doing 5,000 miles changes- you'll be ok. i live where it gets below zero at times and i like to do extended oil changes. i run amsoil with a bypass filter set up. i go 20,000 miles between changes. it basically comes down to dollars and sense- and what you are trying to accomplish- extended oil changes?, more engine protection?

 

I switched from 15-40 to 5-40 Rotella synthetic. Cold starts are alot easier and the motor is quieter while warming up. Average MPG is up .5-1 mpg over the last 20,000 miles. I have been changing the oil every 7,500 miles with a Napa 7620 or 7620XE filter. Rotella 5-40 is $16.24/gallon at Walmart.

 

According to the studies i've read you will get 1- 1 1/2 % fuel economy gain with a 5-40 over a 15-40. The syn guys will say you will get 2-3% using syn as well. syn tranny and gear oil helps too.

 

I picked up .5 mpg switching from 15/40 to 5/40 synthetic. Upped my change interval to 10,000 from 5,000 and the cost is about the same.

 

Synthetic with a bypass filter will save you a bundle in oil. I ran my last truck for 140,000 miles changing filters every 5000 miles and toping up the oil. I sent oil samples to the lab every 20,000 miles to be sure everything was ok and it was. Check Amsoil for everything you need to do this.

 

If you plan on extending your oil intervals, then you realize the benefit of using sythetic. I definately agree that for cold wx ops, the syn 5W-40 is better. However, if you are changing oil in the 3-5K range and plan to continue to do that, switching to synthetic will increase your oil change costs while not gaining you a whole lot.

 

Just changing oil from 15-40 to 5-40 will increase your MPG? How? I need all the help I can get to help with that $4/gal diesel price.

 

How it does it I could care less, all I know is that I get better fuel mileage by using it. I went from Delvac 15w40 to Rotella 5w40 and got a 0.50 mpg increase, when I went to Amsoil 5w30 HDD and I saw an increase of 0.60. So by switching to synthetic oil I gained a total of 1.1 mpg compared to using Delvac 15w40 dino oil.

 

I don't doubt that's possible, but could it be your engine was still breaking in, and thus your mileage improved a bit? (I don't know how many miles on your truck when you changed- maybe the engine was already well broken in.)

 

I switched from 15-40 to 5-40 Rotella at 57,000 miles.

 

Walmart Roteela Synthetic is the way to go. So if you go to a fast lube place most let you bring your own oil. I also saw.50 MPG and starts alot nicer on cold mornings

 

im a stickler so when i did the first oil change when i bought it(53k) i used synthetic. doing an oil change this week, plan on throwing rotella 5w-40 back in it again with a fleetguard filter. runs smoothe, and i did gain a couple mpg's doing so.

 

i've changed from regular oil to Royal Purple i've noticed a little bit better mpg but i have a stiff foot also

 

The weight difference (15w vs 5w) is the cause for increased mpg. I saw the same increase, and noticed cooler engine temps in the summer and the truck starts like it's 50 F in -15 F, increased from 5000 - 10,000 change interval. I will be changing filter at 7500 and change oil at 15,000 this time and see what oil test shows.