Engine/Transmission (1994 - 1998) Help with switch to synthetic oil

[Northrunner]

A friend (Ford diesel) tells me he's noticed a slight improvement in MPG after switching to synthetic oil. I've been using Rotella T 15/40 in a stock 1998 12 valve truck for years. A switch to Rotella's synthetic would be easy for me as it's locally available. For years I've gotten about 15 MPG, recently a best of about 18 MPG during an all freeway trip.



Any thoughts/suggestions from you all will be appreciated.

Thanks...

 

[ETavernier]

Northrunner,

I cannot comment on the improvement from experience as I have always used synthetic. I would expect modest increases in MPG maybe . 5 to 1 mpg. However the oil does a better job lubricating, withstands the stress in the diesel engine better, and will increase the longevity of the oil, thus decreasing the frequency of oil changes. The benefits outweigh the increased initial outlay.

Eddie

 

[LandShark]

The biggest difference you will see will be in cold weather (below 25F) starts. No more bucking and white smoke. I did the same Rotella 15w-40 to 5w-40 at 90,000 miles and have no regrets.

I had a start last week after sitting all night at 0 degrees and had a smooth easy start.

 

[hsmith]

Isn't there an issue with seal leakage on older engines {mine incl} when switching to synthetic?

 

[SRath]

I like synthetics, and that's what I use. But I have also experienced aggravating seal leaks with Mobil-Delvac synthetics in everything I have used them in, which is everything from racebikes to lawnmowers; trucks to cars. In every case, switching to Amsoil has alleviated many of those leaks. So, yes, imo the seal leak worry is justified, but it seems to be brand-specific. When I think about it, Amsoil may be the only synthetic I have tried that did not cause excess seal leaks, but there are far too many to claim I have tried them all. Maybe there is something else as good or better. It certainly can't be more expensive.

 

[Skydiver]

A friend (Ford diesel) tells me he's noticed a slight improvement in MPG after switching to synthetic oil. I've been using Rotella T 15/40 in a stock 1998 12 valve truck for years. A switch to Rotella's synthetic would be easy for me as it's locally available. For years I've gotten about 15 MPG, recently a best of about 18 MPG during an all freeway trip.

Any thoughts/suggestions from you all will be appreciated.
Thanks...

I now pronounce you as "officially switched".
Now, wasn't that easy. Will you run 10k miles between changes? I do.

 

[edgeman]

I would suggest that you go with Amsoil... . I have run both Rotella and Amsoil and I have noticed a difference in fuel milage between both synthetics. They are both good oils though. Love my synthetic oil and no it will not cause any leaks on older, high milage engines! Enjoy the difference! P. S. it will save you money in the long run with fewer oil changes!

 

[MisterBean]

Well...

IMHO, when I originally had my 01 QC SWB 4X4, I completely switched to Amsoil throughout the truck at 15k miles from brand new. I never had ANY leaks ANY WHERE and I easily went 15k miles between oil changes.

Then I lost my mind and traded it in. Insert butt-kicking here... #@$%!

So, I HIGHLY recommend keeping your mind and switching to Amsoil...

Mark

 

[Dr.Bob]

I use RP in everything, mileage went up 1-2.

 

[HEMI®Dart]

I would suggest that you go with Amsoil... . I have run both Rotella and Amsoil and I have noticed a difference in fuel milage between both synthetics. They are both good oils though. Love my synthetic oil and no it will not cause any leaks on older, high milage engines! Enjoy the difference! P. S. it will save you money in the long run with fewer oil changes!

I second Amsoil. I used to run their 15w40 Synthetic Marine oil. Then they came out w/ 5W30 Series 2000 Heavy Duty Diesel oil. To me surprise the wear metals in the "ligher" oil were about 30%-50% less than the 15W40. I run it year round. I don't tow.



I go 17,000-20,000 miles between oil changes. Or 1 year. Amsoil Bypass. Change full flow filter every 6 months and the analysis always comes back "suitable for continued use"



GREAT STUFF!

 

[edgeman]

I second Amsoil. I used to run their 15w40 Synthetic Marine oil. Then they came out w/ 5W30 Series 2000 Heavy Duty Diesel oil. To me surprise the wear metals in the "ligher" oil were about 30%-50% less than the 15W40. I run it year round. I don't tow.



I go 17,000-20,000 miles between oil changes. Or 1 year. Amsoil Bypass. Change full flow filter every 6 months and the analysis always comes back "suitable for continued use"



GREAT STUFF!

I agree with this completely. My father owns a 1990 non intercooled 1st gen and he sold it to our neighbor over 7 years ago. We just recently picked it back up for a plow truck and I went to pick it back up and it fired right up. From what I know it still has the Amsoil in it that my dad put in! There is no wear to speak of in the engine, transmission, or diffs. The only problem is the Transfer case. Amaizing! That also had the oil bypass filter on it!:-laf

 

[fest3er]

I install the Amsoil dual remote bypass unit on my truck at 60K miles and filled it with Amsoil 15W40 at the same time. I have not drained it since. That's 11-12 years and 210K miles.

 

[KB0OU]

I think you should leave well enough alone, if it aint broke don't fix it.

Keep running the 15/40 Rotella.

 

[macdaddy]

I think you should leave well enough alone, if it aint broke don't fix it.

Keep running the 15/40 Rotella.

I have to agree with this, even though I use Royal Purple. You will still have to change it as often as the Rotella, I do.



Mac

 

[Dr.Bob]

Mac did you ever have your RP tested?

 

[Hammer]

In some 250k on my truck with synthetic oil used since I bought it I can honestly say I have seen little or no mileage gain by using it. However,it sure does help alot with cold weather starts and it was nice to still see the cross hatch in the cylinders both times the headgasket was done on the truck. One was done at 150k and the second one at 225k.

 

[HEMI®Dart]

I checked the valve lash. Waste of time.



#2 exhaust was tight

#3 intake loose

#4 exhaust tight

#5 intake loose



Loose or tight = . 002-003 +/-



Did it run any better? NO!: -laf

 

[HEMI®Dart]

I never thought Royal Purple was a top-tier PAO Synthetic like Amsoil. I could be wrong.

But if it works keep using it.

 

[SMorneau]

I don't rack up miles fast enough to justify the Amsoil that I used to use. It would be getting changed due to time and not mileage. I do think the synthetics give better mpg's but when its really cold it seemed to make more difference to have synthetics in the transmission, xfer case, and differentials.