Why did highway MPG drop from 70 to 68 to 66?

[ElectricTroy]

The 70 dropped to 68 when Honda added the air conditioner.

What made it drop from 68 to 66?

[jsanford]

I don't know, but A/C is supposed to be really taxing on the engine. I know I've noticed a difference in pickup immediately with all three cars I've owned so equipped when the A/C kicks in--the Insight most of all. I've never had a car with freon A/C, so I don't know if this has always been true or just since '95 when freon-based air conditioners were phased out.

I've also had mechanics cluck over the placement of the A/C unit in smaller cars, snuggled up against the warm engine block. Maybe that affects performance as well?

[Delta Flyer]

If you recall a thread from several months ago, I use A/C as supplemental light breaking.

[james]

Well, sheesh! Air conditioning takes power. That power has to come out of the gas, therefore your mileage drops. I'm just surprised that the drop is so little.

[Rick]

Are you running the air or not when you get this drop? Consider this, the 2000 Insight was rated 70mpg highway only because enough of them were shipped without AC that they were tested without AC. Then in 01 they started installing enough factory AC's that they had to test the car with AC so the mpg went down to 68 for the highway rating. This loss comes from the slight added drag of turning the AC compressor, even when not engaged, and the fact that it's a lot of extra weight.

If your running your air and only loosing 4mpg I want to know how your only loosing that. I usually see 10 to 15mpg hit in the summer. Plus also consider your probably getting your first winter gas around now anyways.

[Tim Maddux]

I'm pretty sure that Troy is referring not to what he sees when he drives, but to the US EPA estimates of highway mpg for a 5spd Insight, which dropped in the manner he describes from year to year (or two). I forget the exact years but I know my 2000 was rated at 70mpg and the latest are rated at 66mpg.

[ElectricTroy]

Yeah my specific question was:

Why did the EPA rating drop from 68 to 66? What did Honda change?

Hi ElectricTroy:

___The 70 for the 2000’s to 68 for the following 01’s, 02’s was because of the A/C install. That accessory does create drag even when not running. The 03 and 04 drop to 66 hwy might have been because of an update or similar but I have never read anywhere what the update was? The ECU updates themselves (supposedly for emissions?) have not harmed my little beauty’s fuel economy but others in the Honda-Yahoo groups say it did.

___Rick Reese, I believe you were attempting to avoid the 03 on up ECU update for this exact reason so if you have anything to add, ElectricTroy would probably appreciate it.

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:2p1jjdoy]Waynegerdes@earthlink.net[/email:2p1jjdoy]

[ElectricTroy]

Originally Posted by xcel

The 03 and 04 drop to 66 hwy might have been because of an update or similar but I have never read anywhere what the update was? The ECU updates themselves (supposedly for emissions?) have not harmed my little beauty’s fuel economy but others in the Honda-Yahoo groups say it did.

From what I've read at honda-hybrid, the ECU Update reduced battery usage. That would affect stop-n-go portions of the highway test and reduce the MPG.

Hi ElectricTroy:

___No one in the Yahoo Honda-Hybrid groups knows for sure what the ECU updates have done other then that it was an Emissions recall according to Honda. A pack SoC/charge algorithm wouldn’t effect highway mileage since you aren’t on the pack while on the highway nor would the EPA’s highway test be effected either? Go with what makes sense first … until proven otherwise anyway

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___[email:3mo9668g]Waynegerdes@earthlink.net[/email:3mo9668g]