Has anyone who has tried synthetic oil actually seen a change in fuel mileage? If so any recomendations on oil brands.

 

You'll find a ton of info on this if you do a search. I'm switching to Rotella Synthetic 5w40 on my next change.

 

No, but for me its about drivability. My truck runs noticably better in the winter because of SYN oil. That would lead me to believe, that if it starts, runs and sounds better it may be running more efficiently. But I dont keep that close track to know for sure. There are too many variable things here to be sure ie. weather if and what I am pulling, driving conditions.

The big thing is the protection it offers over DINO oil. It won't break down under high stress/heat. And it still flows when its cold (thats the part thats important to me). I don't think you will see a big change in the numbers. A lot of guys that talk about fuel mileage (I think) can make MPG numbers look the way they want. I do it with my wife all the time.

I bought an exhaust system and told her I would expect to see 2 MPG better. $1100 for the MBRP duel exhaust (sounds cool, looks great and I love it) and I test the fuel mileage on a trip to Anchorage pulling a 5X10 luggage trailer. She is pissed because we got the same fuel milage we got last year when we drove to Anchorage in the summer pulling out 34' 10,500 lbs travel trailer.

She was expecting great things. At this point she doesn't want to hear about the fact that our diesel will never run very efficently when the outside temps are below zero. Or the head winds, or the fact I was driving 75 - 80 mph this time.

There is alot of knowledge on this web site. But when it comes to accurately measuring fuel mileage.....I think we all have a problem.

1. It is impossible to fill your fuel tank to the same exact level two times in a row at a gas station. Very few of us would have the means to ensure accuracy here.

2. The same driver, would have to operate the same vehicle, in the same terrain, at the same tempurature (exact same weather conditions), carrying the exact same weight, with the same amount of idle time in between, using the same speeds and rates of accelerations.

 

mnm has made several good points about improved driveablity in cold temps and the difficulties in comparing apples to apples because of conditions, drivers, load etc. Although I was able to transcend the barriers in conditions when comparing mpg with conventional oil vs synthetic in my previous 6.0 towing my old boat: I would frequently drive 360 miles roundtrip with the same load (7,400 lbs), same driver, same truck on the same route in very similar conditions with conventional oil and then I switched to 5W40 M1 synthetic oil. Each time my average was 11.8-11.9 mpg with 15W40 conventional oil. After switching to synthetic, the average was 12.7-12.8 mpg. Almost 1 mpg increase. Not huge but every bit helps. This was based on the overhead LOM which would have consistancy in the parameters which establish the mpg calculations.

IMO any of the major brand 5W40 synthetics which are rated CI-4+ or CJ-4 will work well in the 6.0 PSD. My choice is Mobil1 but I'd run Rotella or Schaeffer if there wasn't any M1 readily available.
FWIW I use 5W40 synthetic year round including very heavy towing in the summer with excellent oil analysis results

 

I agree with all of the above posts. I finally got Rotella synthetic back in my truck last week after running Motorcraft 15W40 for the last while since the dealership put it in after installing headstuds. I can't say for sure that I get any better mileage, but I do know that the cold weather starts in Lake Tahoe last week were much better than they had been down here near San Diego (and it's not cold here). I did get 19.2 mpg heading home at 75 mph on Sunday, but that might be related to the tailwind that I had for a while. I bought this truck with the intention of having it for over 10 years and I just feel that running synthetic will help me get there and I have an oil analysis to back up my hopes.

 

I just went from Rotella T to Rotella synthetic on my last oil change. While I have not filled up yet, I can say that it does seem to start easier(has not been real cold of late to test cold starting) and run smoother. As far as mileage, I did have slightly more miles when the fuel gage hit the marks but I don't have enough data yet to make a definete call on it. I do know that I will be using synthetics for the next several oil changes, I have two cases of Schaeffer 9000 Supreme in the garage...

 

I don't know where Schaffers9000 would be availible up here

 

I treid Schaeffer's 9000 5W40 and didn't really notice any mpg improvement. It didn't hold up very well towing my 5th wheel so I went to their 15W40. It did ok towing but I wasn't that impressed with it. OCI done by Blackstone at every oil change. Just had the motor and trans out for a bed plate leak. I'll put about 2000 more miles on the Ford oil and then switch to Royal Purple 15W40 full syn.

The biggest thing you can do for better mpg is slow down. At 67 mph I get about 21 mpg. Pretty big increase from about 19 mpg at 70 mph. Like I always say, use the best oil you can afford.

 

I'd be interested in your UOA on Schaeffer if you could post them. I am also very curious to see the Royal Purple UOA's. There just aren't that many for RP posted here or on BITOG.

TIA

 

Bismic,

I've sent you my blackstone reports on the Schaeffers. I just changed and used Mobil Turbo Diesel 5W40 this time. I plan on running it about 5 or 6 thousand then send a sample to Blackstone but change to Royal Purple.

I have about 100K on my truck and have decided that everyone has an opinion about their favorite oil, but very few base that opinion on actual tests. I'm going to change brands of oil at every change for the next few changes just so I can have some comparative results. All my driving is the same - very heavily loaded on the interstates so the results should provide a pretty good comparison.

BTW, next time I change and use an oil stocked by walmart, I think I'll let them do the job. I've been using a local (to Austin, TX area) chain and I didn't ask how much they charged, just told them to change oil and filter and specified mobil Diesel Turbo 5W40 and genuine Motorcraft filter. They charged $278. I learned my lesson.

 

$300 for an oil change!!!!!!!!!!!!!!!!!!!!!!!

You should press charges for grand larson!

 

Thanks for reminding me Jim - I will post them!! I just plain forgot!!