Jodi's Colorado vs. California gas milage

About 11 years ago I had an 83 Toyota Corolla. At the time, they were adding MTBE to our gas in CA, and I noticed that when I went to visit a friend in Reno NV, I would get about 5-10 MPG better milage from the non MTBE gas in Nevada than my normal California gas. When I got a new car, the gas milage between the two gas formulas was nearly the same.

I know MTBE has been banned in CA since 2004, but I believe we still use some oxygenate additives. I have no idea what additives if any are used in Colorado gas, but maybe this has something to do with Jodi’s gas milage differences in her older Civic.

If anyone has ever driven to any extent in LA they will have the same problem. When I am not in city traffic my Volvo gets 29-30 mpg. When I go to LA it drops to 19-20.
The reason? Without measuring it, I estimate that at least 30% and possibly at times 40% of driving time is spent idling at traffic signals, or stopped on the freeway.


At first I thought that maybe while she was shooting her documentary she might be carrying around a bunch of camera gear and/or people. However, I still can’t figure out why (if she is accurately measuring on a tank by tank basis) it would take multiple tanks of gas for the mpg to decrease. I’ve lived in SoCal and I can definitely believe that it is simply the stop and go of normal traffic there, but it still doesn’t explain the slow degradation.

Whats MTBE

see also:

Methyl-tertiary butyl ether


Jodi was surprised that her mpg upon entering LA would deteriorate over time. She tried different gasolines, etc, but it slowly dropped and reached a steady state. It would improve when going back to Colorado and out to Joshua Tree, which puzzled her. She understood that cars would get poorer mileage in bumper-to-bumper traffic. But what I think confused the situation was that she was reading AVERAGE mileage and thinking it was INSTANTANEOUS mileage. I’m sure she has an algorithm that calculates average mpg over say the past 1000 miles or so, and it wouldn’t plummet upon arriving in LA, but instead deteriorate over several tanks of gas. If she ONLY drove around LA at 3 am, she would probably get great mileage!

I lived in Los Angeles for 12 years; and was a limo driver there as well for a while. My thoughts while listening to you guys banter; ‘someone is tapping her gas tank’.

My theory is that, as Jodi spends months in LA, she becomes more and more fed up with the city, and drives more and more aggressively—jackrabbit starts and sudden stops. So her gas mileage is just an indicator of her degree of existential angst.

Perhaps she’s filling up with E10 Ethanol mix in LA but not in Colorado. Experience with my 1996 Dodge Caravan is about a 10% drop in mileage E10 vs non-ethanol. I think there might a higher percent E10 stations here on the west coast. It could explain the gradual drop, too: with partial fill-ups, gas dilution would take some time.

Perhaps she's filling up with E10 Ethanol mix in LA but not in Colorado.
But she does mention that she switched brands of gas. I would think if she?s paying attention to what brand she?s putting in, she?s paying attention to the grade of gasoline. And she?s talking about going from 30+ mpg all the way down to 18. Even E85 (if you have a flex-fuel vehicle that can handle it) only causes a 25-30% decrease in mileage.

Partial fill-ups could explain the gradual drop in mileage, but I don?t think 10% ethanol could possibly explain a decrease of that magnitude.

I believe that this explanation is correct. Arco, for example, offers an 85 octane “reformulated” product that performs badly in some cars. By comparison with the intermountain states, gasoline on the Pacific coast is required to be oxygenated, and I think the manner in which this is done varies by suppliers. In any event, I can smell the difference and also notice it in the car’s performance and mileage. I live in Idaho, where gasoline is still mostly gasoline. I first encounter “California gas” in Hermiston, Oregon, where there is the first Arco station. The gas is cheap, and still smells like California gas.

I think Click and Clack came close to the solution asking about tire inflation and the possibility that tires were leaking. But Jodi said MPG resumed at higher elevations. Didn’t hear anything about ever checking tire pressure. I think her Colorado tire pressure has dropped at low altitude LA. Jodi should check her tire pressures in both locales.

Considering her stated pro-environmental stance she should also consider inflating her tires over Honda’s recommendations, but not to exceed the max cold PSI printed on the side of her tires.

As others have commented, but the EPA denies (they say its only 2%), I too have seen a 10% hit using E10. Its not a certain thing but every unexplainable hit to MPG was with E10. IIRC California mandates E10.