Just figured it up from 1999-2002.

9,709 miles of mineral oil......10.83 MPG average
10,002 miles of synthetic oil...10.96 MPG average

All types of driving, all weather. Some trailering with both types. Mineral for first 8k and some in the middle. Synthetic after 8k and some in the final part.

Quaker State 5w-30. Mobil 1 5w-30.

1999 F250SD V10 4x4 Regular cab, 3:73 Auto

Thought you might find it interesting. I did. Synthetic didn't do much for my overall mileage.

 

A little over 1% is definitely in the believable range, though I know that my mpg can easily vary over 5% just due to speed and other variables.

 

I use synth oil for improved reliability and reduced oil changes.

 

I tried 5w-30 Havoline synthetic for two years in my 99 Ranger 4.0L & 94 Taurus 3.8L OHV engines & saw no increase in city/urban mpg & a "best of show", 2.2 mpg increase in hwy mpg, but only on the Ranger & this was at 55-70 mph over a 340 mile round trip.

I had just changed the oil & filter the night before the trip, gassed up at the same station, same day, same pump, facing the same way & filled at the same pump speed. So I was reasonably sure of my 2.2 mpg increase results.

I thought I could see about .5 mpg increase in tow mpg on the Ranger while using the synthetic recipe, but imo this figure was so low, as to be too close to "noise" in the calculation, that I've all but disreguarded it.

So as most of my driving is city/urban & I could not measure any mpg increase in that type of driving, calculated at every fill up, on both vehcles, over a two year period, I no longer use synthetic & am back to dino Havoline in both vehicles.

Now if I drove the Ranger mostly on the hwy, I'd pobably opt for synthetic in the Ranger 4.0L OHV engine, because of the "real" increase in hwy mpg that I've measured on several trips.

Just my expierence & thoughts on my 2 engine, two year trial!!!!

 

"Energy Conserving" 5W-30 is the same in mileage tests, regardless of base oil used. That fact was just proven once again. The myth that synthetic engine oil saves fuel is based on using the original Mobil One (5W-20) verses the typical 10W-40 conventional that most everyone used in 1972.

Friction modifiers have been added to all "Energy Conserving" motor oils and that makes a differnce, but has nothing to do with the base oil group. Another thing that modern conventional oils have is a greater resistance to oxidation, "thickening", which could have made a mileage difference if you extended drain intervals.

Jim

 

yeah, I have been using syn since 1980. I keep complete vehicle logs including mileage and averages so I have a lot of history to look over.

It is really hard to pin down mileage improvements to syn since the daily variation of mileage is a lot. I have had 17mpg in my car on one tank and the next is 22 all depends on how much street driving I do.

Also a new engine is a bit tight and doesn't give best power and mileage for a long time. I recall some Car and Driver magazine tests where they found that some engines don't reach their peak for 30,000 miles or more.

So yes the syn probably does make a difference in mileage, but it is not accurately measurable by us unless you have a test track and equipment and drive the same everyday with the same weather etc.

I use syn due to claimed better temperature tolerances and better drain intervals. I don't expect mileage to make much difference.

Just my opinion,

Jim Henderson

 

If someone drives the exact same route and the traffic is not bad, over time those small variations should cancel out and a trend could emerge. However, other effects (i.e. just an air filter change) may have more effect on mpg, so one need to be very careful when trying to interpret the results.

Usually, I don't even bother calculating my city mpg; only do that on trips outside of the urban areas. My daughter lives exactly 300 miles away with most of the driving on a wide open freeway (I-90) and rural highways, so that's a very good opportunity for mpg tests. I stocked up on Havoline (6 cases) but Amsoil is currently 20% off in GI Joe's, so I may do the unthinkable, and for an experiment's sake, I buy some for one oil change.

 

I choose to use synthetic oil, because I can afford to. Simple as that. The added OCI is a plus, but my main reason, I guess is for cold start pumping, with a 5w30 oil such as Royal Purple or Mobil 1. RED LINE also makes a great product.

I've seen those who scoff at the cost of a synthetic oil VS dino (which dino oil costs are getting closer to some full synthetics), they complain it costs too much, but will gladly purchase 3 cartons of cigarettes (or more) every 2 weeks at Costco or Sam's Club.
Go figure? While I'd gladly use a dino oil, such as Chevron Supreme, (and do occasionally) I like the benefits of synthetic oils. I simply chose to protect the moving parts of expensive emmision controlled engines, with a small part of my "fun" money, after the bills are paid. Bottom line.
Ed

 

How much petroleum is used in a pure synthetic oil?

 

Mr. Incredible... if you're comfortable with math, you can find a website that will direct you on how to run some statistics to determine whether or not there is a high probability of the difference between your two conditions is statistically significant. If it isn't, then no conclusion can be drawn regarding the difference. Otherwise, it would be believable. I've personally seen many occasions in the manufacturing world where if you have enough data points, even very small differences in averages can be overwhelmingly believable.

Just another $0.02

 

Math is not one of my hobbies. Statistics I leave to others. Testing methodologies were not followed. That said, the 2 sets of 10k miles were as close to the same as I think anyone could have short of making it so.

What kind of synthetic was Mobil using in late '99 to late 2002? I don't know.

Just presenting the facts I have, making the conclusion that M1 and QS of that timeframe were so close as to be indistinguishable for purposes of MPG. Thats all.

If any other conclusions are drawn by others, that's their buisiness.

 

2000Expy

It depends on the type of "pure" synthetic, but generally more than conventional. Esters are made by reacting alcolols with acids, but very few automotive synthetics are ester-based. PAO and Alylated Napthelenes are made from crude oil and use more energy to manufacture than conventionals, hence the greater cost. M1 is PAO, AN and Esters, has been for many years, not the straight PAO of 1972.

I'm currently running a Group III synthetic, Coastal, $1 a quart on clearance from Autozone. Since I keep records of every drop of gasoline and the mileage, I can calculate mpg averages over the long haul. I would be surprised if it is any different than Chevron Supreme when this run is concluded. When I ran 10W-40 Syntec in the BMW vs 15W-40 Delo, I was expecting a mileage improvement. None measured.

Jim