Old-timer getting worse mileage - because of older battery?

[bonbayel]

I got my original Insight on January 1, 2001, way before there were automatic versions. We really felt like pioneers.

Soon after I got my Insight I got a job with a very long commute over a couple of mountains, going from 1500 ft to 3000 to about 0 in Palm Springs. I was averaging over 70 on the way to work and had a life-time mileage of 63.2 by the time I left job 9 months later.

Since then I have alternated between no job or work from home, and thus a lot of town driving with nasty stop signs, and short-term jobs with clogged freeway traffic. We used my car for trips to LA on weekends and a couple of long trips to San Francisco, but now that my husabnd bought a new Prius we use his car for those trips.

My lifetime mileage is down to about 60.1 and still dropping. I rarely get my tank mileage about 50 any more. Part of the difference is probably that I'm not new and enthusiastic, although most of the good driving habits are pretty automatic. (I get better twon mileage on the Prius than my husband does, but I rarely drive it!) Then, too, the local driving is often in areas with stop signs and fewer traffic lights, and our town is on a good grade up to a mountain, so you coast going south and use 3rd gear going north.

But I've been wondering if some of the problem is the age of the battery? An engineer I was talking with implied that batteries perform less well with time.

[Resist]

The best mileage gains are not the result of "Good" batteries, so it's safe to assume bad batteries don't cause worse mileage. Unless you are in a charging condition all the time. But I think maybe your tire pressures need to be checked and more attention to driving mpg skills.

[Shriner]

I know this is not a popular belief on this forum, but I am convinced that old batteries are exactly why so many people are discovering reducing MPG averages (I do not believe the 12V battery has anything to do with it).

My car has over 90,000 miles on it, and the battery charge indicator rarely ever seems to be over the halfway mark, anymore (unless I am doing a lot of driving on the interstate). I have concluded that the batteries just do not hold their charge as well as they used to. When the car was new, it was apparently easy to keep the level in the top half of the battery charge indicator. I am tempted to spend a bundle on new batteries just to prove this theory. If the car is spending all its time trying to charge the battery (please don't start a thread regarding driving habits, tire pressures, etc, since this is not what I am talking about), then it is not utilizing the batteries during driving. Makes perfect sense to me, although it is a major bummer.

The averages keep dropping as the batteries get worse at keeping the charge... only people with failing batteries are noticing this

[Insightful Trekker]

Resist hits a bull's eye

The best MPG comes from not using the IMA systam at all. Of course this discounts the city drive cycle.

Honda's IMA system is basically there for increased power. The gasoline engine is undersized and tuned for maximum MPG (when driven to take advantage of the ability) the IMA system is simply there as an electric "supercharger" (power boost). And as resist stated unless your in forced charge too often (which is a consequence of aging IMA batteries) then the IMA system does little for maximum MPG.

It's difficult to say what bonbayel's specific "problem" is in relation to her lower attainable MPG with the information posted.

HTH!

[stompper3]

Bonbayel... I feel your pain.
I have about 120k on my 2000 insight. I experienced the same problem and I always focus on driving to get the most miles per gallon. At around 30k I had problems with the O2 sesors. They changed these (Honda later said they were not bad) and a "computer" at the time. Since then I have been in the low 50's. I have gone from 65-70 mpg to now 47-48mpg.
Finally my IMA light came on and finally a honda dealership was able to "diagnose" the problem. $5400 later, a battery and two computers, things should be better?
Not a chance! I'm getting 45-47mpg. The battery guage went from full at the dealership to around a quarter or less and wont go up. However, I have noticed bigger "spikes" on the mpg guage since the new computers.
I am wondering if there is a problem with the power generator for the battery?

[InvisibleGold]

Guys,

I would take a look at the basic maintenance items that seem "unnecessary" on the Insight. I just got an older car (115,000 miles) and barely (if ever) would get it over 60mpg. Last weekend I adjusted the valves and have averaged 70+mpg for the three of the last four trips. Sure it sounded like it needed to be done - but not as much as you might think.

In contrast, "regular" cars seem to need new spark plugs and valve adjustments every 15,000-30,000 miles. I am leaning toward taking care of these things one by one to see what difference they make.

-John

[Jivko57]

I think the reduced MPG may be is coming with the cars age and higher mileage and is a consequence of the engine wear and /or of out of adjustment valves.

I bought a 2000 manual insight ~ 1.5 months ago at 196k with ltmpg 52.1.. My mpg for the last 5k is about the same, I tried hard but cannot go over 63mpg on a single trip with constant efforts (above average). In lean burn my speed is falling with a rate of one mile each second so I cannot keep lean burn more than 20 sec at a time. I start from 65 mph and after 20 sec my speed is down to 45 mph which is not safe for the highway that I am using as traffic is keeping 70 mph on average.

I have driven many different cars for the last 20 years and consider myself an experienced driver (probably more than 350k miles driven in all kinds of weather and road conditions)

There is no way my present engine to have 70 hp + 13 hp from the ima motor
If I had to guess I would say it is gravitating around 65% of its design power. On the other side I have never driven a 2000 insight in new condition so I cannot make a comparison.

One thing: I cannot keep 65mph in 5th gear without the help oh the ima system! Is this normal for a 2000 MT insight. Did you have to rely on the IM just to keep 65mph on a level highway in 5th gear when your insight was new? Or even now if you have 50-60k miles on the engine?


So far I had changed the spark plugs (b type) , the oil, air filter, new EGR valve,( no plate cleaning though ) and a am using premium gas only.

I do not carry any extra weight in the car.

And I drive in energy conserving way., 45 to 65 mph , conserving momentum, tires inflated to 44 psi, no A/C, light fethered foot etc. so far my best mileage is 63 for 25 mile run and best tank is 54 mpg…..

I do not wish to change the engine prematurely, but will be glad to do something that will improve the power of the car's engine and the MPG. Any ideas?

[Hybrid-Battery-Repair]

Originally Posted by Shriner

I know this is not a popular belief on this forum, but I am convinced that old batteries are exactly why so many people are discovering reducing MPG averages (I do not believe the 12V battery has anything to do with it).

I've found that lots of customers with failures that do not result in constant recals, actually get WORSE mileage when they get their battery. This appears to be because they develop a lead foot with all the new torque that is available. After a while (and practice), they start getting excellent mileage again.

Originally Posted by Shriner

My car has over 90,000 miles on it, and the battery charge indicator rarely ever seems to be over the halfway mark, anymore (unless I am doing a lot of driving on the interstate). I have concluded that the batteries just do not hold their charge as well as they used to. When the car was new, it was apparently easy to keep the level in the top half of the battery charge indicator. I am tempted to spend a bundle on new batteries just to prove this theory. If the car is spending all its time trying to charge the battery (please don't start a thread regarding driving habits, tire pressures, etc, since this is not what I am talking about), then it is not utilizing the batteries during driving. Makes perfect sense to me, although it is a major bummer.

The averages keep dropping as the batteries get worse at keeping the charge... only people with failing batteries are noticing this

What you need to realize is that the battery capacity drops over time. This is normal and as long as all the cells drop in unison, the battery will work fine. The power output of the battery does not drop. A weak battery will still pump out a sustained 50 amps of power like a fresh one - just for a shorter period of time.

A brand-new battery (6.5Ah) will provide about six minutes of full-on assist (if the assist is not reduced due to heat). A weak battery (let's say 3Ah) will provide about 3 minutes of the exact same level of assist. A battery that is at death's door (1Ah) will still provide bursts of a minute or so.

How you use the minutes of assist determines your mpg. On the highway you rarely use the battery, so any diminished MPG has to be for another reason.

In your case, I'd suggest doing a battery relearn so that your SOC gauge matches the range of your battery. It won't change the battery, but the scale will line up properly.

[02insight]

My 02 Insight (5spd), currently on its second battery (1st one replaced at 120k), now at 175k, seems to be getting weak also. But with my style of driving (trying to use the least amount of assist), I can manage about 65-70mpg on highways, and around 55-60mpg in city.

When I do utilize the battery, I notice that it has to keep playing catchup and whatever amount of benefit the engine gets with the assist, it loses it again with the amount of charging and background charging that it has to do.

I also tried driving without the battery (simulated by the clutch switch mod), and I was able to do around 45-50mpg in city (no autostop), and around 65-70mpg highway. Which isnt that bad, so I know when my battery dies, and I cant afford another one, I will probably drive the car without battery for a while.

[3-Wheeler]

Originally Posted by Resist

...The best mileage gains are not the result of "Good" batteries, so it's safe to assume bad batteries don't cause worse mileage. Unless you are in a charging condition all the time....

Just want to emphasis, that an out of balance battery can cause allot of background charging, and that will cut into your gas mileage.

Jim.