The perils of ethanol

I drove 450 km across the mountains from Kelowna to Abbotsford yesterday morning, then back in the afternoon. Same route (freeway all the way, light traffic), same conditions (sunny and cool in the am, sunny and warm in the pm), same speeds (120 km/h plus or minus).

Going out, I had a tank full of pure gas, no ethanol. I used half a tank and filled up before returning, this time with 10-percent ethanol in the gas. Regular grade both times.

Trip out: 10.2 liters per 100 km. 23.1 mpg.
Trip back: 11.9 liters per 100 km. 19.8 mpg.

I think I'll be avoiding ethanol from here on.

Anybody else with this kind of experience?

I don't think ethanol affects MPG as significantly as that. I mean when I load up the E30 tune on my Speed3, my MPG drops by 2. You lost over 3 MPG on the same OEM tune. I think it must be driving related. Maybe the drive back was more challenging for the car.

finch204 said:

I think it must be driving related. Maybe the drive back was more challenging for the car.

Click to expand...

Seconded. I think it may have more to do with the elevation difference (Kelowna is 344m, Abbotsford is 38m). From Kelowna to Abbotsford, you're on a decline, and on your way back, you're on an incline. The car definitely has to work a bit harder on the trip back. It's also possible that headwinds and crosswinds could have had some minor effect on your mileage as well.

With that said, E10 has been stated to decrease fuel economy by 3% (https://www.eia.gov/tools/faqs/faq.php?id=27&t=10).

Ethanol also has some other side effects as well (https://www.theglobeandmail.com/glo...lem-with-ethanol-in-gasoline/article29103634/). Whether these side effects are occurring in modern vehicles or not, I'd rather not risk it and instead, stick with ethanol free. If I could get 87 octane ethanol free, that's what I would be fueling up with. Unfortunately it's only available in 91 here.

You've got to run the test in the opposite direction before making any conclusions. I agree that it's probably more incline related, altho ethanol certainly does hurt mileage.

When I drive the highway to the nearest "city" [CX-5], I consistently get around 33 going "downhill" and 27 going back "uphill". And the elevation difference isn't very much, only about 600 feet over 15 miles.

roadrutz said:

I drove 450 km across the mountains from Kelowna to Abbotsford yesterday morning, then back in the afternoon. Same route (freeway all the way, light traffic), same conditions (sunny and cool in the am, sunny and warm in the pm), same speeds (120 km/h plus or minus).

Going out, I had a tank full of pure gas, no ethanol. I used half a tank and filled up before returning, this time with 10-percent ethanol in the gas. Regular grade both times.

Trip out: 10.2 liters per 100 km. 23.1 mpg.
Trip back: 11.9 liters per 100 km. 19.8 mpg.

I think I'll be avoiding ethanol from here on.

Anybody else with this kind of experience?

Click to expand...

E10 gasoline mix has about 95% of the energy content of pure gasoline. Something else is reducing your mileage, not just the fuel.

Yes, Kelowna to Abbotsford is a net decline of some 300 meters (1,000 feet), so the trip back is obviously a net climb of the same amount. But I don't think that is particularly relevant as the trip goes like this: After leaving Kelowna you climb steadily to just under 1,750 m (5,700 feet; Pennask Summit) then drop back to 600 m (2,000 feet) at Merritt. From Merritt you climb to about 1,250 m (4,100 feet; Coquihalla Summit) then drop to almost sea level at Abbotsford. So it's hardly just a gentle climb/decline. The road is curvy freeway the whole way -- perfect conditions for the CX9!-- except the last 80 km into Abbotsford, which is straight and flat.

The trip home did take about 15 minutes less, so possibly I was driving a tad faster. There was no discernible wind. But still, according to the car's computer, my fuel economy dropped by 3 mpg on the return trip, and the only significant difference I can see was the use of ethanol-laced fuel. I wonder if altitude has any impact on the energy difference between ethanol-free and ethanol-laced gas?

sm1ke: I'm lucky; my local no-name gas is ethanol-free in all grades. [<-- Maybe not. Apparently gasoline in Canada has to average 5% ethanol which is why regular always has 10% ethanol -- whether noted or not -- mid-range has 5%, and premium usually none.]

Luckily here in Montana we have ethanol free premium (91 grade) just about everywhere so that is what I will be running from now on. Average MPG's for the first 4000 miles on premium with 10% ethanol was 22mpg combined. I'll see if there is a difference. I just wish the price difference was not so large here.

Miles per gallon is only part of the equation. What really matters is the cost per mile. Higher mpg is a loser if it costs more per mile.

I have not seen any damage in a modern engine using E10.

On my GTR- I get about 18mpgs w/93 pump (e10). On e85- I'm lucky to get 11. Same type of driving.