11% FE improvement with diesel fuel additive

[Night_Sailor]

I have a 2001 Silverado K3500 D/A dually. In my first 107,000 miles, my best ever fuel economy was 15.9 mpg. I achieved this twice on cool days on smooth open highways. 15 mpg was typical, and 13 mpg on winter blends.

I'm rebuilding an old aluminum framed/skinned pickup camper, and my goal is to be able to carry another 3500 lbs and keep my fuel economy up above 15 mpg.

I've done a lot of research and learned a few things:

1) That bigger exhaust systems don't do much unless you are at high throttle settings. I don't plan to tow 15,000 lbs or strain my Duramax if I don't have to. These seem like a waste of money.
2) I also researched air filters and found that free flowing air cleaners help, but also let in a lot of dirt, while the factory air filters do a tremendously better job keeping dirt out of these motors. I'll keep my stock air filter
3) That synthetic lubricants don't have a significant effect either, although I intend to try that.
4) I did find research that fuel additives do improve fuel economy. The best reported was bio-diesel blends. I plan to try that as soon as I can find a good source for this. Next best is a product called Opti-Lube XPD. This is a cetane booster and lubricant. From what I gather the new low sulfer diesel fuel does not have adequate lubricants in it and over the next few years, bio diesel blends will be common. In the mean time I started using Opti-Lube XPD and saw an immediate jump in fuel economy to 17.75 mpg on mostly highway at 62-65 mph, with some city. I was impressed. Tires were stock sizes and non aggressive tread patterns.

I next cut back my speed on the parkway and saw a further improvement. Even using air conditioning, at 55mph, I saw my new best record, 18.82 mpg on 51.4 gallons. I think 19 mpg might be achievable if I keep my speed at 50 mph.

All these were measured with full tanks driven to the warning lights or a bit beyond--53 gallon tanks with typical fills at 47-52 gallons. In the past my typical range was 700-750 miles, 650 in the winter. Now I'm routinely getting 900 miles on a tank, and once 969 miles! (32 miles past the low fuel warning light) I plan to try their oil additive next.

Last trip at 65-70mph yielded 16.81 mpg. I can honestly report a gain of between 6% and 11% improvement due to the additive alone; the rest I attribute entirely to slower driving.

My motor is turning the same rpm/s with less work/fuel needed to maintain these speeds, and it runs much quieter for this reason.

I hope some of you other diesel guys will give this product a try and report your results.

[euromodder]

Originally Posted by Night_Sailor

In the mean time I started using Opti-Lube XPD and saw an immediate jump in fuel economy to 17.75 mpg on mostly highway at 62-65 mph, with some city.

Did you change anything else at (approximately) the same time ?

A 6-11 % improvement at the low MPGs that you're seeing, is a massive change in fuel consumption.

[elhigh]

It's nice to see this not in the Unicorn Corral. 11% is a more realistic claim than some of what gets touted there.

Start a garage entry for your ride. It's possible some of the (more talented than mine) eyes looking over your results will spot a detail that can steer you to more positive results.

Finally, go look at Diesel Dave. I don't know what the hell he's doing but he's got a truck not too dissimilar to yours and is pulling in 50mpg. I think that might be what Lone Starr would get if he poured concentrated Schwartz into the fuel tank.

[UFO]

I have not done any research or testing of biodiesel blends myself, however I still find about a 10% difference between mostly pump diesel and mostly B100. My VW TDI (ALH) consistently returns 10% better mileage with B100 -- I have done my level best to calibrate distance into my Scangauge and measure my B100 as accurately as possible. That is the one difference I cannot eliminate in my comparisons since I pump my own B100 with a home-fabricated station and a gauge that measures in quarts.

It contradicts what most claim about biodiesel because of supposedly lower energy content, but I noticed a mileage drop when ULSD was introduced. I think the new diesel fuel is about the same energy content as my B100 now, so the main fuel difference could simply be the higher cetane.

[Diesel_Dave]

Originally Posted by Night_Sailor

1) That bigger exhaust systems don't do much unless you are at high throttle settings. I don't plan to tow 15,000 lbs or strain my Duramax if I don't have to. These seem like a waste of money.

Agreed. Bigger exhaust is better, but the effect is very small unless you're running near max power.

Originally Posted by Night_Sailor

2) I also researched air filters and found that free flowing air cleaners help, but also let in a lot of dirt, while the factory air filters do a tremendously better job keeping dirt out of these motors. I'll keep my stock air filter

I'd keep the stock filter too. Oak Ridge National Labs did a study with diesel and found the effect of air filter restriction on fuel economy to be quite small. Like the exhaust, less restiction is better, but the effect is quite small.

Originally Posted by Night_Sailor

3) That synthetic lubricants don't have a significant effect either, although I intend to try that.

I found a good benefit to switching to 5W-30 synthetic (5-10%). One thing to keep in mind is that the effect of synthetics will be greater in colder weather and with shorter trips (more cold oil operation)

Originally Posted by Night_Sailor

4) I did find research that fuel additives do improve fuel economy. The best reported was bio-diesel blends. I plan to try that as soon as I can find a good source for this. Next best is a product called Opti-Lube XPD. This is a cetane booster and lubricant. From what I gather the new low sulfer diesel fuel does not have adequate lubricants in it and over the next few years, bio diesel blends will be common. In the mean time I started using Opti-Lube XPD and saw an immediate jump in fuel economy to 17.75 mpg on mostly highway at 62-65 mph, with some city. I was impressed. Tires were stock sizes and non aggressive tread patterns.

I next cut back my speed on the parkway and saw a further improvement. Even using air conditioning, at 55mph, I saw my new best record, 18.82 mpg on 51.4 gallons. I think 19 mpg might be achievable if I keep my speed at 50 mph.

All these were measured with full tanks driven to the warning lights or a bit beyond--53 gallon tanks with typical fills at 47-52 gallons. In the past my typical range was 700-750 miles, 650 in the winter. Now I'm routinely getting 900 miles on a tank, and once 969 miles! (32 miles past the low fuel warning light) I plan to try their oil additive next.

Last trip at 65-70mph yielded 16.81 mpg. I can honestly report a gain of between 6% and 11% improvement due to the additive alone; the rest I attribute entirely to slower driving.

My motor is turning the same rpm/s with less work/fuel needed to maintain these speeds, and it runs much quieter for this reason.

I hope some of you other diesel guys will give this product a try and report your results.

I don't put too much stock in FE claims from fuel additives. That being said, it is somewhat fuel system dependent. Older fuel systems aren't as robust as the newer common rail systems, like mine. I did an A-B-A on Howe's Meaner Power Kleaner and found no difference whatsoever. Recently, I've started using some Schaeffer's Diesel Treat, but my intention is more to keep the fuel system clean than it is to get better FE directly. Keep in mind that even 5-10% gains are tough to reliably see in real world driving because there's som much variation in weather, trafic, etc.

As to biodiesel, I haven't run it in my truck, but I've burned lots of it in an engine lab on the dyno. The energy content is lower, but only about 11% for pure B100. The cetane rating typically is a little higher, so in some rare cases, blends like B5 & B20, have actually been shown to have a very slight FE inprovement (<5%), but even that is fuel system dependent. You may have economic and/or environmental motivations for running biodiesel, but don't expect any mileage improvemnt from it.

In the mean time, good luck and start keeping a detailed fuel log if you haven't already.

[oil pan 4]

I know of owner operator truck drivers swear by diesel kleen power service in the grey jug. They claim it makes a difference of hundreds of dollars in fuel consumption over a cross country round trip.
But they are only claiming a 2% to 4% FE improvement on 6 to 8 mpg machines over thousands of miles.

[Tesla]

I use a little (0.5%) mineral 2-stroke oil for extra fuel lube as well as a diesel fuel additive to keep lines clean, have not noticed difference in fuel economy, although bottle states "may improve FE".
I think the additive can help with bad fuel or if system is a bit blocked, but if system and fuel is good then additive is more of an insurance type thing.

[elhigh]

I've seen lots of mileage claims dip a bit when drivers switch from petrodiesel to bio. Then, as often as not, they state that their mileage "comes back." I think that could be attributed, first, to the lower energy density of biodiesel as a couple of other commentators have noted, but the much higher lubricity of bio frees up some wasted horsepower by slowly dissolving deposits in the engine and keeping all the bits moving more freely.

I don't have a diesel - I wish - but I have read a few pages where the shadetree mechanic would clean parts by soaking them in diesel, and soak the really TOUGH parts, or the seized engine, in biodiesel. Just drop it in and leave it. Come back in October, it'll be loose.

[kafer65]

I think you have very good handle on things. I've been through the air filter and change to synthetics on a gas 4wd Silverado and I didn't see any improvement in mileage. Synthetics may show some improvement in winter. That was a good point. I did, however, see a substatial improvement after putting a three inch straight through muffler and headers, surprisingly.
I have noted a small improvement on my 06 TDI with fuel additives. There can be a huge swing in mileage related to fuel quality though. I usually hang at 40mpg in summer and 38 in winter, but I got 32mpg once on what I'm sure was a poor quality fillup once. I got 46mpg 90% highway this year since I found a very good diesel supply. It gets tested often for contaminants. Much of that jump was because I'm in mixed driving mostly.

[Arragonis]

I tried a Cetane booster additive for a tank in Helga. That tank was improved but I couldn't put it down to the additive itself vs. weather, temps, wind, or maybe I was just getting better at FE driving.

The cost of the additive was about £8 for the tank which at the time was costing me £60 so it cost me more than 10% to go maybe 3-5% more - so I never continued.

The local "motor parts" shop here in the UK in Halfords - if they have it on offer next to the tills I might buy a bottle but at full price not a chance.

Bottom line - I suspect the OPs technique improved together with warmer temps - but every gain is a gain.