2003 Honda Accord 4 cyl gas mileage on the highway

I say up front i ahven't used cruise control in years, except for once last week. My vehicles don't have it, i don't use it. I used it on my wifes work van, a 96 T+C. Before this, my last experiance was with a

03 buick century back in 03 (a rental car).

Basically, whenevre it droped below the set speed, it opened the throttle to what felt like 20%, and carried on until the set speed was reached. Personally, i'd fluctuate a bit more, run it 3 or so over, let it run 3 or so under, and repeat. The vehicle seemed to surge as well, as it moved into acceleration mode. and it never went over about

2500rpm, avoiding the peak torque area (which is the most efficient area)) although whether this was more a fact of the cruise control, or the slushbox, i don't know.

These large and drequent instances of throttle usage are not efficient However, the wife loves the cruise control. i've asked her to make a not of how far and how much fuel she used in the van today, and when we do the route again, i'lm going to go with her, and drive as i normally do, to compareThat'll be at least a week away though.

So you're saying you have very little experience with cruise control.

I also noticed that you avoided answering my question, so I'll ask it again:

So you're keeping your throttle at exactly the same position, manually, and if you go up or down a hill and your speed changes dramatically, so be it?

Is that what you're doing when you drive, to avoid the throttle movements that are "inefficient"?

My Datsun roadster had a manual throttle lock. I'd get to cruising speed, pull the knob, and there I was... Mechanical Cruise Control.

Same thing for a few bucks on motorcycles, some sort of flip-lock on the throttle.

On roughly level ground, it worked just fine. A freeway overpass would knock some speed off, and down the other side would overspeed, but overall it was a pretty decent thing.

Logically, one might do the same thing with an electronic cruise control. As my Civic starts up a grade, I have two choices: I can let the cruise control maintain the speed, including over 5000 RPM, or I can kill the cruise control. If it's a long grade, I let it run whatever RPM it wants. If it's a minor grade, I kill it.

If there was some tolerance, allowing the speed to drop, programmed for a typical overpass, cruise control could be more efficient. People without cruise control are probably losing speed at that point anyway, so they would never notice.

Oh, I agree. I would like the option to be a throttle lock instead of a cruise lock.

And with computers, it ought to be that easy.

I'm saying i have limited experiance, but with that, i pay a lot more attention to what its doing - its not something i take for grated, and ignore as a backgroud part of driving'

no, i'm not. If you read what I said, I vary the cars speed, work with the grade (and with the road thats comming up - something NO cruise control can do) anticipate, etc.

Cruise control programming is very simple

10 IF speed

To drive efficiently, you must drive smoothly, with no sudden speed changes, and in harmony with the othre road users around you. A cruise control takes no notice of any enviroment except the one its driving over at that second, and has no way of detecting other road users. It in no way attempts to use the engine most efficiently, so HOW can it be driving most efficiently?

i was kinda disappointed in the mileage my 98 civic CX got going from LA to laughlin nevada and back.

if i would have taken it easy and cruised with traffic at 70-75mph, i might have gotten more than my usual 32mpg.

but no- i had a lead foot. some of it wasnt my fault.. some grades are so steep i had to drop it into fourth and floor it just to keep at

80mph. 5th gear was useless, the car couldnt keep up. speedo kept dropping, even with it floored.

and of course, i had the A/C blasting in that 114 degree desert heat, too. the mojave desert gets damned hot during the day.

so to reiterate: thats uphill, several thousand foot climbs (2000-5000 feet at a time), A/C blasting, pedal to the metal in 4th gear, doing

80mph uphill. and the temp gauge stayed below halfway! thank gawd for mobil1 5w30.

downside? 25mpg.

I can think of at least one possible way *if* the car is an automatic. It is possible (though I do not know for a fact) that the OEM could factor in the CC in the torque converter (TC) lockup routine. Generally the TC locks up at a certain min rpm and for a range of throttle positions. It might be programmed to note that if CC is engaged, throttle-based drivability concerns will not be as big a deal at lower rpm settings. Thus it might lock it up at non-normal speeds resulting in a more efficient transmission.

Anyway, it has been my experience that CC probably beats my mileage. But one factor may be that if I have CC engaged, I'm driving slower than I would otherwise.

As to the modulating throttle, I think it is a fallacy that this markedy decreases MPG, unless done so *aggressively*. At least in a manual where the TC doesn't come into play. Contrary to what you might infer from your high school driving instruction, an engine is actually more efficient at higher (but not max) throttle setting. Accelerating doesn't consume more fuel, braking does! (well, accel does, but it just stores it in the kinetic energy of the car where it is available for later use). And yeah, faster driving means higher rpm and air drag. Both of these result in increased frictional losses.

I believe.

I get 32-33 per tank doing mostly freeway commuting, some at 80mph, some at 5mph, most somewhere in between, a little city driving at each end. That's by myself, no air, mostly, and with the automatic. Flat route, btw.

Been driving a mixed route with a 500 foot rise through the Sepulveda pass recently, ought to measure my mileage again, doesn't seem all that different.

J.

Dunno if this last paragraph was directed at me or not. Engine is most efficient at arond its peak torque area. (at least for non vtec engines) I'm not sure about them, having not had much experiance of them. I personally didn't learn about anything at high school (since i'm not american, and thus never went to one) but what i learnt about cars, i learnt in my teens, working on my fathers rally car, and doing the old economy rally's. Those were fun, slingshotting the car around the peak torque area, and using a saab freewheeling unit in between.

I think that is close, but at peak torque, most if not all engines go into fuel enrichment. So, they won't be terribly efficient there. Highest efficiency is typically about 20% or so below the peak torque for that rpm judging from the fair number of brake specific fuel consumption maps I've seen. That's still a very high throttle setting which you won't see in typical cruise.

Possibly a difference between US and EU tunes

Why not keep up with the pace of traffic rather then being an hazard?

Not neccessarily. Cruise control increases the throttle opening for any slight incline. Practiced fuel economy drivers will let a little speed bleed of on modest uphill inclines and then let it build back up going down the other side.

For *most* drivers, cruise control can improve fuel economy. However, for those rare drivers who have studied the art of fuel economy maximization ... ya can do better.

John

BZZZZT! Yellow flag scam possibilities. Rust is not a reason to replace rotors. Insufficient thickness, deep groves and warping are all possible reasons for replacement.

Old story, old scam.

John

Exactly what does this entail? And doesn't traffic interfere with your careful anticipation? People doing a constant 50 around here are in danger of being crushed by Yugos running on one cylinder.

It was probably the A/C and the desert heat that sapped a lot of the power. In 4th gear, while climbing mountain (in Hamshire & Vermont) I'm able to maintain 105 mph, but that's on a nice cool (65 degree) day with no AC equipped. If you're racing up a hill and your speed is under 100mph, 3rd would be the preferred gear, instead of 4th. While climbing a particularly steep hill in 3rd gear at high speed, frequently I'd have to pass on the right (those pick-up drivers have a lot of attitude, especially when there's a small car bugging their ass on the left lane).

30 mpg is about right for aggressive driving situation and slowing the speed down to 50 mph would return a huge improvement on fuel consumption (like 40 mpg or 50mpg on a cool day with fairly level grade).

Also, after 250,00km of driving, I've yet to see my temperature gage go beyond the 2/5 mark. The big engine compartment with lots of free space helps.

Pars

98 Civic Hatch

Seems a mile or two better!

J.

JXStern wrote in news: snipped-for-privacy@4ax.com:

i got 16km per litre last week on the highway in my 99 accord