CARBOB energy content.
 

Apparently, CA uses a different oxygenate blend than the rest of the nation uses, as well as cutting everything with 6% ethanol. Does anyone happen to know what the difference in energy content between CARBOB and BOB is? I'm curious because I stumbled on something The Toecutter posted.

I've noticed similar effects with CA gas. My old mazda truck always ran stronger and got better FE with non-CA gas. Motorcycle all of a sudden was running really rich when I moved back to WA. Whatever oxygenates they use cause carbureted engines to run a little leaner, that's why motorcycle manufacturers have different carb specs for california models. I definitely noticed that CA gas produced less power, requiring more fuel to go the same distance.
Sorry, no help on the particulars but I seem to remember more benzene.

Wow, I guess that means the 47.4mpg on my last tank is really 52.4mpg? That would put me in the top ten, wohoo!

While there certainly could be a difference in mileage between CA gas and 49 state gas, the post Toecutter made on his Prius indicated he was getting much better mileage in Denver. I wonder if this could have something to do with the altitude and how the ECU in the Prius handles the difference in pressure? If the gas was the same, you'd almost think the car would get worse mileage at high altitude, but who knows?

I'll try to do some research on this, but I do know that CA changes gas formula from winter to summer. It'd be interesting to know the difference between these two types as well.

When do they change from summer gas to winter gas. is there a spicific month or is it temp related

I thought that the energy content would be the same as any other E10 blend and that the main difference was that in CA they were using a low sulfur content gas. Also didn't all gas to low sulfur this year along with diesel?

Specific month.

It would seem to me that being at high altitude would increase your gas mileage. Less wind resistance, lower pumping losses, etc...

And for the OP, I cannot think of any reason for CA gas to have a much lower energy content. No reason at all. The gas in Denver should have been an oxygenated winter blend, so it's not even a conventional vs rfg thing...

Hello -

There was a fellow here by the name of koinos :

Hi, another Paseo from Long Beach CA
https://www.gassavers.org/showpost.ph...00&postcount=1
He only posted a few times, so maybe he is gone. But if he is lurking, then I'll bet he would know.

CarloSW2

dont forget about less power. My family and i took a vaction to colorado in elevations of 7000+ feet above sealevel while we live in a measily 600 feet above sealevel. our van (96 Aerostar)seemed to be a noticeable difference(huge one might say) in power. so it may not get better MPG because you will have to press the pedal harder to get the same force out...i would think.

California banned mtbe starting 1/1/04 as a oxygenate, now they use ethanol, supposed to be 5.7%. but can be from 4% to 9% depending on the fuel supplier.
zpiloto is right they recently switched to low sulfer, but I think there is more to it than that.
Carbob has limits on lots other chemicals like benzene, xylene,Toluene,Ethyl Benzene,Nhexane,cyclohexane to name a few. adding more or less of some of these could change how much energy the fuel has.
I'm not sure the oxygenated gas is doing what its supposed to do though.
Carbob will be changing the max. oxy % on 7/1/07, the max oxy content is going from 0.25 to 0.009

That would theoretically also improve FE due to reduced throttle (pumping) losses Bill was referring to (assuming you didn't also use lower gears more).

Generally speaking, cars driven at higher altitudes should get better mileage than cars at lower altitudes (all else being equal).

Depending on temperature difference rolling resistance may increase or decrease, and aerodynamic drag would decrease because of lower pressure/density. Pumping losses shouldn't change as long as the percentage of oxygen per other stuff (Nitrogen, etc) doesn't change since the only drop is in pressure, not oxygen content iirc. I'll PM that chem engineer, and keep on looking online.

edited due to idiocy. ;)

Found a CA gov website that claims CA gasoline has 111,500 Btu per gallon. 0nl1nec0nv3r510n dor c0m says U.S gasoline has ~124,900 Btu per gallon. Which is 12% difference in energy content! :o

Edit- yup
Not only do we have to pay ~30-40 cents more per gallon, we get about 10% less energy! Which translates to about 60-70 cents more per 124000 Btu.

EPA website list RFG with ethonal blended fuels at 111,836 so CA not that far off then the rest of the country that has winter blend it just that CA runs it year around right?

well it is a van (ranger truck frame. engine, and most likely the same trasmission) it is an automatic + mountains = shifting around a bit when goin up hills/mountains but down the hills/mountains we just put it in either 3rd or 2nd and let the engine do the brakeing.

I don't think it's the winter blend since that only varies 1.7% per gallon (Avg energy content per gallon, summer versus winter) for most of the US, but the RFG like you mentioned. It's widely used in CA, but on a county by county, not state basis. It seems like if a driver lives in one of the blue areas they use it.
https://www.epa.gov/otaq/rfg/images/rfgmap.gif
Winter RFGs/summer RFGs show a respective 3% and 1% drop in relative energy compared to the same conventional gasoline. However, one thing that's still not covered is the difference between CA and federal oxygenated blend... For instance, in CA if 10% (the label on the gas pump states up to this figure) ethanol were used, the energy content would drop by 3.4%. This is required by law in order to get the oxygen content at around 2%, iirc the AQMD is supposed to have the Oxygen at .2% in a few months, so I still have no clue as to what the difference between CA RFG, other RFG, and conventional gasoline is... Talk about a PITA. :confused:

I applaud your research, I spent about 1/2 hour on the weekend and the best I could find was a description of the many chemicals that were banned and what they are replacing them with. Reminded me of how much I hated organic chemistry.

I just gave up. What I find interesting is the large swing in the allowable BTU for gasoline that alone can make a difference. From the EPA site:

Energy Content (btu per gallon)



Minimum Maximum Difference



Summer 113,000 117,000 3.4%

Winter 108,500 114,000 4.8%

How many stations get the maximum allowed you think?:rolleyes:
Any way good luck on your quest?

Heh, yeah... if there's ~4% difference between stations, who knows? I just think that anecdotal blurb may be onto something... May just be a lark. I'll keep on looking in a bit, I should configure a comp for my uncle. mrmad, thank god ochem wasn't a requirement for me. ;)

Well, the last spike in mileage must have been caused by switching away from the winter blend, since according to this, we switch back to regular CARB gas in March
Course, that's only a .5mpg difference for me, so I'm wondering where the other ~2mpgs came from? Probably the drop in average speed, or it could be the AFM mod? Too bad I can't use this gas tank for a comparison, ~15 minutes of idling at 1000rpm and ~10 minutes of reving to 3000rpm in N should shave at least 10% off of my mileage figures. Shows me for leavin' my truck's parking lights on! :D