Unocal R99 Renewable Diesel in 7.3L PowerStroke

[Timerider]

Has anyone else tried the new "green" diesel fuel from Unocal 76 in their 7.3L (or other) PowerStroke SMB and noticed that the engine sounds a lot quieter?

This past weekend my wife and I fulfilled some family obligations 300 miles away in SoCal, and the 76 station next to my favorite Del Taco drive-thru had a funny green badge on their sign out at the street, advertising "renewable" diesel.

After doing some on-line research on the www.76.com website, which was mostly a bunch of of generally un-helpful flowery weasel-words from their marketing department, I decided that at $4.99/gallon (the cheapest diesel around was $4.79/gal.), I'd roll the dice and fill up. This added 31 gallons of the "green stuff" to the 15 gallons of regular diesel plus a bottle of Stanadyne diesel additive that was still in our 46-gallon tank.

We got about 45 miles (≈3 gallons) down the freeway on cruise control when I noticed that I wasn't having the usual conversational difficulties with my wife. I asked her if the engine sounded quieter to her, and she said that she had just been noticing the same thing. Things stayed that way for the rest of the 300 miles to home.

Am I crazy and/or is this just wishful thinking on my part?

I'm gonna get my dB meter and audio spectrum analyzer and do some definitive testing as a "sanity check" just as soon as the opportunity arises (i.e. the next nearly-full tank that I buy in SoCal).

So, has anyone else tried this new "green" 99% renewable diesel from Unocal 76 and noticed that it's quieter, or noticed any other differences?

[BW3340]

R99 is a good product, it it's essentially a fully synthetic diesel that is made from soy beans and animal fat. It will burn cleaner and more evenly so I could see some noise reduction, your oil will also stay cleaner as well because of it. I've never ran it in my van (only because they would fire me for stealing fuel) but we tested it extensively at my work (million mile engines) and from what I understand its superior in both lubrication and cetane value

[1der]

Good to know, I will keep an eye out for this option and give it a try. I regularly use the B20 when traveling between SoCal and San Francisco as it is available on I-5 at a few convenient locations.

re your 31 gals added to "15" in your "46" gal tank.

If this a Transfer Flow "46" gal tank w/o any vent/harpoon mods then you likely did not have 15 gals in your tank but rather 10 to 11. If the mods were made then you might be closer to 46 gal fillable capacity, otherwise the most I was able to add to ours was 41.5 gals after just starting to suck air.

[ShuttlePilot]

I have heard the same as BW3340 states about the R99 fuel. Before this conversation takes off let us acknowledge that there is a difference between R99 "renewable" Diesel and the regular "biodiesel" blends seen as B2, B5, B20, B100. The difference is in the production process, which the R99 dose away with the ethanol component of the B blends. I would run the R99 in my 6.0 but I try to limit/eliminate the amount of bio fuel blend in my diesel.

- Eric

[Glenn P.]

It is funny you mention the use of R99 and the reduced engine noise. I have run the fuel in my 2002 7.3L F250 pickup and noticed the same thing! It didn't seem like a huge difference but on the freeway driving home with just myself in the vehicle is seemed quieter. I figured it was just one of those things as with a different fuel type you are just looking for a difference and if their isn't one your brain invents one. I was using ARCO R99 but I would think this is coming from the same suppliers and made to the same standards regardless of the station you buy it from or the hype the retailer adds.

I have run several tanks now through both my 7.3L and my 6.0L and all seems good. I did not notice the engine noise reduction on the 6.0L however but perhaps my R99 ratio to dino diesel was not as high as I was not on E when I filled it up. Hard to say. I would be very interested in your test results with a db meter. Please post that when you complete your testing.

I still believe the biggest difference between cheap fuel and expensive fuel is the quality of the window washing squeegee!

[Timerider]

Originally Posted by 1der

Good to know, I will keep an eye out for this option and give it a try. I regularly use the B20 when traveling between SoCal and San Francisco as it is available on I-5 at a few convenient locations.

re your 31 gals added to "15" in your "46" gal tank.

If this a Transfer Flow "46" gal tank w/o any vent/harpoon mods then you likely did not have 15 gals in your tank but rather 10 to 11. If the mods were made then you might be closer to 46 gal fillable capacity, otherwise the most I was able to add to ours was 41.5 gals after just starting to suck air.

Ray,

You are of course quite correct in bringing up the subject of the "harpoon" mods to Transfer Flow tanks because the concentration of R99 diesel fuel in my "test" could either have been about 67% (15 gal. of Dino-Diesel present prior to fill-up), or about 76% (10 gal. of D-D), or somewhere in-between.

(Glenn, I really like that "Dino-Diesel" expression, and hope that you don't mind my borrowing it for use here.)

But either case suggests that a noticeable reduction in engine noise, i.e. "diesel clatter", may have occurred with fuel that was significantly less than 100% pure R99 diesel fuel. This implies that others wouldn't necessarily have to suck their tanks "dry" before adding R99 to try this experiment for themselves.

Unfortunately, there's only one Unocal station "near" me, and it's about 35 miles away in a mountain ski-resort community (read: near-monopoly situation), so their prices are correspondingly sky-high. So my further testing will have to wait until we visit SoCal again in our SMB. (Getting 50 MPG in the Prius is hard to pass up - but I'll admit, it can't make waffles.)

I'll try to arrange taking some baseline acoustic data while burning the last of a tank of mostly Dino-Diesel on the freeway near the 76 station in SoCal on our next "family" trip down south in the Silver Kitten, and will then refill with R99 and repeat the acoustic testing on the same stretch of road. This may be difficult to coordinate, but it seems worth doing.

Also, an update:

After researching "cetane" on Wikipedia last night, and sending a question to the folks at Unocal 76 about R99 diesel fuel, to my surprise I received an E-mail this morning - followed by a phone call no less. Unocal said that their new renewable R99 diesel consistently exceeds the upper limits of the ASTM D613 cetane test method (max. of 65) and the ASTM D7668 test method (max. of 70), and that this greatly increased ignitability (i.e. cetane rating) is the difference in the R99 fuel that accounts for the lower noise level that I may have noticed with our 7.3L diesel SMB. But even though their own testing yields even higher cetane ratings than these standard tests can detect, Unocal says that they can't advertise about this because the testing wasn't done according to either of these recognized ASTM standards (although there are also other recognized testing methods).

Later I found a really interesting paper on Cetane by the National Renewable Energy Laboratory (NREL) in the USA that explains how ignition delay caused by lower Cetane Ratings causes a sharper pressure peak (and more engine noise) due to a greater accumulation of unburned fuel prior to its ignition, which makes sense when you stop to think about it. I guess the two-stage fuel injection of the PowerStroke diesels and higher cetane fuel are two different approaches that address the same issue.

Perhaps someone on this forum with more knowledge about diesel fuel testing and n-hexadecane (a.k.a. cetane) than I have could explain this better.

[Glenn P.]

I just topped off with some R99 at lunch today having this conversation fresh in my mind from this morning. Another very noticeable difference with R99 is the lack of foaming! It is very nice to be able to fill up and just have to burp the tank a little and NOT have to wait for the foam to diminish. I've done the Hutch and Harpoon mods on my F-250 with the 7.3L and filling it with R99 is really, really nice. The van with the 6.0L has a Sportsmobile 40 gal tank and filling it with dino or bio diesel blends is not fun due to the foaming but R99 is a much nicer process.

So if you are like me and like to the see the fuel at the top of the filler neck before you quit pumping, give R99 a shot and you'll be pleasantly surprised at how much easier a fill up is.

[Orv]

In general the biodiesel blends have better lubricity than modern low sulfur diesel, which is good for mechanical diesel injection pumps. I remember when biodiesel was new seeing an engine manufacturer study that investigated it as a lubricity enhancer; they found that a 5% biodiesel blend with jet fuel had better lubricity than regular diesel. (Jet fuel was chosen for the test because it has almost no lubricating qualities of its own.)

[vandiesel]

Weird but I had (key word bad memory) the entire back story on renewable diesel. I worked with a guy here in Portland who had the patents that were created by a couple at Texaco (think) that allowed veg oil to bind with diesel. It was all part to help meet demands for epa as well as make renewable (bio) asphalt blends. This is the first I’ve heard of it commercially dispensed. We were working on converting crow Indian crops from hard red wheat to camolina seed and do the blends in the field without splitting the oil into its ester parts. Old news now.

[Orv]

When I lived in Michigan back in the 2000s you could get B20 (20% biodiesel blend) at a fair number of gas stations. In Washington that was less common but there were biodiesel co-ops that sold it, usually B95 or B99.