I need better economy!

[rendyx]

My SHO is by far the least economical one I have seen yet on this forum. Some complain they fill up at 250 miles, but I'm at nearly 1/2 tank with only 108 miles on the odometer. This gives me roughly (starts Calculator ) 12MPG! Strangely, it dropped from about 21 to 16 a couple months ago rather quickly. Here is just about anything I can think of which has happened since the old days of 21:

1. Temperature dropped outside. First, a little, now a bit more. But will that really hurt the economoy this much?
2. My PS fluid and water levels are both a bit over the full lines.
3. I let my car sit for a while to defrost a couple mornings, for about 15 minutes a couple times. Now I'm starting to just let it sit the needed couple minutes to I don't run the motor bone dry.
4. I have tried running through a bottle of Berryman's B-12. Perhaps the problem is not in the fuel system?
5. I run 93 octane fuel already, which I have heard will improve my economy.
6. More on the water level: it is leaking somewhere. All I can think of related to this is the extremely long defrost times. And BTW, what would cause frost on the inside of the windows?

Any ideas? I'm stumped and going broke. I think I'm going to go back to my quick lil' MPG booster: toss in $5-10 gas between fill ups to make it look like I am using less gas!

<small>[ December 08, 2002, 09:40 AM: Message edited by: rendyx ]</small>

 

[jthomas68]

A fall in gas milage can be caused by faulty o2 sensor(s).I think there is a bit on shotimes about it,and i`m sure more will chime in here.

 

[yamahaSHO]

If you were to say your engine was running warm I would say check the ECT, but since you said it is running cool jthomas68 is probably right in saying the O2 sensors could be bad.

 

[rendyx]

Sounds like something I may investigate. I checked the SHOTimes article, and I have a question. Where are all of the O2 sensors I should test? I've never really played with them much, and I know little about them besides what they do. Second, I noticed another article on the site about the ISC and high idle speeds. I don't really have an idle problem, but the car does do some heavy bucking when I let up on the throttle too quickly. I've always thought this was the normal amount for the car, but this article makes me wonder. Still, I'm going to look at the O2 sensors first before I start playing with the ISC. Thanks!

 

[sdpatt]

I rarely see posts regarding mileage actually calculate the gas mileage. They usually go by references on the fuel gauge. We all know how accurate that is. If you are going to check your gas mileage, calculate it per tank by dividing the miles traveled (reset te trip odometer at the gas fill-up) by the number of gallons it took to fill the tank (miles/gallon). Due to the uncertainties associcated with filling the tank to the same level each time, this measure is more accurate if averaged over several tanks.

My mileage per tank can vary from as little as 12-14 mpg towing my 18-foot boat, to my normal 15-17 mpg in all city driving, to as much as 26-28 mpg if all highway driving (at a 70-80 mph cruise speed).

As long as the temperature is between the white marks at the top and bottom of the NORMAL range, then the temperature is normal. Actually, the MTX usually runs around the A-L (or even lower) and the ATX runs around the R-A.

The oxygen sensors get less accurate with age and carbon buildup. This can happen and slow down the sensor's responses (rich lean switching) even without setting an error code. The general rule is that you should replace the oxygen sensors at the same intervals as the spark plugs - 60,000 miles. How old are they?

Water vapor condenses on a surface when the surface temperature is below the dew point of the atmosphere near the surface. The vapor will freeze (frost) when the temperature of the surface is below freezing. The vapor in the air in the passenger compartment is from your body, your breathing, wet shoes and melted snow among other sources. If it were antifreeze, by its name, it would not freeze on the window, but still be in liquid form. Check for your coolant leak at the water pump (lower timing cover drip port), radiator end tanks, radiator hoses or heater hoses.

 

[shojuan]

sdpatt:
I rarely see posts regarding mileage actually calculate the gas mileage.

I've noticed this as well! How hard can it be? Just write down your mileage between fillups, always fillup the car, the more consistent you are here the better your numbers will be but as long as you just fill it up you'll get a good average. Figure the difference in mileage between your current fillup and your last, then divide by the number of gallons it took for your current fillup and write it down. Do this each time and you'll have a good average.

Rick

 

[projectSHO89]

The actual fuel guage postion is meaningless for computing MPG... About as meaningful as division by zero.

Extended (more than a minute) warmups will eat your fuel economy.

Using 93 octane fuel will eat your fuel budget up fast and you probably wouldn't notice a difference than if you were running 87 octane. Figure 20 cents per gallon difference. It is not very likely to improve your actual MPG. It does increas your cost per mile substantially.

Fuel containing oxygenates (such as alcohol) contain less energy than 100% gasolne. Something to consider...

Unless you live somewhere that never freezes, you shouldn't be running "water" anywhere in your car. You should have "coolant" which contains "antifreeze". Even if you did live is such a place, you still need something with rust/corrosion inhibitors and WP lubricants in it. If antifreeze is leaking and is getting onto your inside windshield, it will almost never defrost. It will leave an oily film that is difficult to remove with glass cleaner.

Fuel economy is greatly affected by the driver. It's easy to drive like a granny and add several MPG to your average.

Steve