Poor MPG for hypermiling... Maybe it's my tires?

[Slopfrog]

I have a 2005 Kia Spectra 5 (auto unfortunately) which I recently bought for a commuter car, since driving my truck was killing me financially , plus I felt guilty about the pollution and lining the pockets of big oil, countries hostile to America, trade deficits, etc. etc.

Well, the car's first tank got me a whopping 25 mpg, even though virtually all my commute is highway. Which means I was losing money on the deal by the time I paid for insurance on the thing. This led me to try hypermiling.

My first tank after doing so was 30.6 mpg. For a small 4 cylinder car I am unsatisfied... Driving without AC (which in Florida is hot even in December), no defroster, granny starts and stops, coasting in neutral for painfully long distances, 60 mph on the interstate, etc... I don't want to sound entitled to better fuel economy but I was expecting the payoff to be a bit better.

I have a sneaking suspicion my tires are working against me. I have them at 40 psig rear and the max of 44 psig in the front, yet they STILL look like they're low on air in the front. Of course, they're brand new so I'm stuck with them. They're Firestone Affinity and they seem to have sidewalls built of mud. Has anybody else experienced similar issues with tires?

Any other ideas? I need an aftermarket cruise control anyway to save my foot, and since the only hills around are interstate overpasses and bridges I think it will help me a little by maintains better throttle control than my tired ankle can manage to do. Thanks!

[ksa8907]

You might check your alignment, underbody tray would help. Do you try and p&g? It may be better to stay at a steady speed with an auto.

Welcome!

[2000neon]

It may be worth your while to look into an ultragauge or scangauge. That will allow you to get instant feedback about what works and what doesn't for hypermiling. For example, you said you're accelerating slowly, it may be better off to accelerate a bit quicker. Acceleration is the worst for fuel efficiency, so by accelerating slowly you may drag it out unnecessarily long, where it may be better to accelerate briskly and get up to speed quicker.

30+ MPG is still good for a stock car, especially for starting at only 25. You should also look into some simple mods like a grill block, tire spats and an air dam.

[LeanBurn]

What kind of tires do you have currently?

[Daox]

Ditto on the scangauge/ultragauge/something. It will help a ton and pay for itself in a very reasonable amount of time.

However, the car's EPA rating is 21/31. With the cruise set to 60 mph you should be able to beat the EPA rating pretty easy unless you hit a lot of stop and go traffic. I find it relatively easy to beat EPA highway ratings simply by driving conservatively. You will definitely want to continue driving this way, but make sure to check out our 100+ hypermiling tips to get some more ideas on how to improve your driving style. Its not all 'drive like a granny' stuff, and IMO moderate acceleration is better than slow starts assuming you don't use brakes later on.

Mods will definitely help, but I'd try to start beating EPA before doing anything to the car. Its completely doable. It might even be a mechanical issue. Brakes that are hanging up, or a bad O2 sensor can really hurt mileage and don't necessarily cause the check engine light to turn on.

BTW, welcome to the site.

[bestclimb]

ditto on the alignment.

Does the Check engine light behave correctly? On when engine is off but key is on, then goes out after start.

scan/ultra gauge or MPGuino if your car does not already have fuel consumption display. If it does are you getting your mileage numbers from that or from the miles on the odometer and gallons from the pump?

[myrefugeisintheLord]

Learning how to beat EPA via hypermiling takes time too. I didn't see much of an increase for the first year. But then I was having to unlearn how to drive with a lead foot too.

P&G IS helpful with an auto. I only just started doing that this last Summer. And it upped my mileage by quite a bit.

One thing with an auto, is it's ALWAYS idling. In that you can't EOC. So the longer you take to get somewhere, the more it's idling. It's frustrating to me, when I'm in a hurry, I hypermile at a higher speed, and sometimes make it to my normal destination with less mileage, but not by as much as I might have guess it would be. Considering the speed and all. Utilizing aero mods would be a huge help to any auto.

And yes, accelerating faster is sometimes better. Personally, I start from a stop pretty slow and smooth. And about every second accelerate faster and faster. Getting it up to 80-85% Engine Load in a matter of 6 seconds or so. It's enough for about 4 cars to pass me from a stop. I have a heavier vehicle, so I figure it's better to get it started at a slower speed, but once going, I get her up to speed pretty quick.

If you're coasting in N, I assume too that you're sitting at lights in N as well? Keeping it in D with your foot on the brake uses up unnecessary fuel. I also adjusted my idle speed down as low as it would let me. 650 RPMs at a stop. I could go lower, but the RAV has built in precautions to keep me from doing that. Also, when driving I haven't seen the RPMs get any lower then 900. RAVadoodle takes care of herself.

One note about it being hot down there, I have found it doesn't hurt my mileage much, if I have my driver window cracked, and the right back window cracked. It lets in a nice cross breeze that keeps me cooled down.

You're getting a lot of good help! Keep trying and you WILL get there!!

[nbleak21]

Get a fuel monitoring system! It will be the best investment you make.

[tru]

he will have a scan gauge next time im down that way as a test instrument... I really think he needs to go thru the car completely to see that theres no underlying maintenance issues holding him back

I.e.

Air filter
spark plugs / wires
changing to a light synthetic oil at the next interval

(might not hurt to see what the previous driver/owner was getting for mileage)

[sbestca]

I used to have an old Dodge 3/4 ton 4x4 truck when I lived on a local "mountain".
I'd start it up in the morning, crawl 200yds to the crest of the hill and coast downhill in neutral. With the rugged bias ply tires I'd see about 50mph max on the coast downhill.

Well, I bought a lovely set of Michelin radials. That first morning I had to WHOA! put on the brakes as I was achieving 70mph in the old truck. The difference was amazing.

We don't have tires that bad anymore, but rest assured there are gains to be had if you need new tires.