Diesel Fuel Additives

[Mark Rinker]

My conclusion (based on lots of miles, and lots of different additives tested) is that if you are looking for increased mileage / fuel savings to justify the expense - save your money.

On re-read, I failed to make the point originally intended...that is, adding fuel injector cleaner to each tankful is unlikely to provide a sufficient increase in mileage for that tankful, to cover the cost of the additive. However - adding cleaner over time is likely to keep injectors spraying freely, and avoid situations where mileage is negatively impacted, or lifespan of injectors shortened.

Bottom line - I am a believer in (quality) fuel treatments, but its very hard to measure your ROI in a repeatable or meaningful manner.

[DmaxMaverick]

As indicated above, short-term testing is of little value. However, in the long-term, mileage records can be very helpful to determine the usefulness of additives, from an economic point of view. I have used various additives, and combinations of additives, in the same vehicle (2001) over more than 100K miles. My conclusion is (and has been for over 10's of thousands of miles now), the additives I use do, in fact, pay for themselves, monetarily. I cannot attest to any component longevity advantage. That would require a fleet of like vehicles tracked over their lifetime with meticulous record keeping.

For a couple years now, I have been using Power Service (gray bottle) and Supertech (Walmart) TC-W3 two-cycle oil (formulated for liquid cooled engines, as opposed to hotter air cooled engines) at about 8 oz. each per tankful (20-25 gallons). I can see, feel, and hear a difference if I don't use either or both of the additives. The engine is more quiet, smoother, more responsive, and returns better mileage. Period. YMMV, but in my case, it's obvious to me.

[Mark Rinker]

>>> I can see, feel, and hear a difference if I don't use either or both of the additives. The engine is more quiet, smoother, more responsive, and returns better mileage. Period. >>>

Here is a reasonably scientific test - for illustration's sake:

1) Take two brand new, identically equipped Duramaxes off the assembly line, one that will run treated #2, the other to run only 'plain' #2 as a control;

2) We then take 50 Duramax owners (members of TDP perhaps), have them take each truck home for a week of varied driving, cold starts, etc., and after using both trucks - record the one that they believe was running treated fuel;

Hypothesis #1: ~25 would pick truck 'A', and ~25 would pick truck 'B' +/- 5%.

Hypothesis #2: The truck running treated fuel would average slighly better MPG over the entire test period, but its total fuel + additives bill would be higher than the truck running only straight #2, when adjusted for any variance in miles driven between both trucks.

Hypothesis #3: The truck running treated fuel, if these tests were extended to include (500 drivers * 2000 miles) = 100K miles, would be less likely to develop a 'stuck' injector, or encounter injector failure, while the control truck would be more likely to encounter decreased mileage at some point, or even stuck/failed injector(s).


Again, even with a control - its easy to see that BIG variances in driving by the 50 or 500 members, temperatures, terrain, and countless other factors would make an accurate, scientific test difficult if not impossible. With only one truck, its nearly impossible for any individual to make any scientifically sound conclusions - as there is no way to test against an accurate control...

[JohnC]

Gee, all I did was drive the same boring route day in and day out, day after day, week after week, month after month... and record every drop of fuel that went into the engine. My mileage calculations from tank to tank were remarkably consistent. Then I started using the additive and repeated the same process. I think I threw out tanks where I was on a long trip. Probably 20K miles without and 20K miles with.

[Mark Rinker]

- Were the 20K mile tests conducted during the same months, with the same weather? How many gallons of winter blend fuel were burned, vs. regular #2? Same fuel station? Same fuel quality and source throughout the entire 40K test?

- Every Duramax I've owned has recorded slightly better mileage, the older it got - as long as the injectors were in good shape. Never saw >20mpg unloaded with the 2002 until it was on the second set of injectors and nearing 200K miles on the clock. How could this observation effect your results, using your "20K without treatments, 20K with" method, as a control group - especially if you started the tests when the truck was relatively new?

- If you drove your truck 20K miles without any additives, its likely you then had deposits forming - that were lowering your mileage. Start using additives - and you will likely find your way back to your engine's MPG potential, in a few tankfuls. What if you could maintain your mileage potential by adding only one bottle every 3rd tankful? 5th tankful? Only when you begin to see a consistant, repeating decrease in mileage...?

IMO - Meaningful controls for an accurate test of fuel additive ROI are impossible with one truck - or even a fleet of 'similar' trucks.

[JohnC]

a) It was a 6.5, not a Duramax

b) The test was over several years. The truck had 28,000 miles when I started. For the first two years or so I did not use an additive. Then I used Stanadyne for at least the next two years, winter, spring, summer and fall. I did not stop using it. Fuel came mostly from one station over the entire period. Routes and conditions were almost always the same. I recorded every drop of fuel and what type of driving. My mileage was consistent and repeatable. I got (IIRC) 5% better mileage with the additive; just enough to cover the cost of the additive.

c) If the additive was reducing or preventing deposits, so be it. The mechanism is immaterial; the results speak for themselves.

d) I feel it is easier to get meaningful results with one truck doing the same thing over the same routes with the same load day in and day out than with a fleet of trucks driven by different drivers and pulling different loads to varied destinations.

e) I am a trained scientist with a BS, an MS and even an Associate degree, and am familiar with the scientific method. I have confidence in my results.

QED