OK.....

This is really weird:

I bought my HCH almost 3 weeks ago.

Since I got it, I've been trying to get MPG performance. Well my first tank gave me 35 MPG and my 2nd gave me 37.... The best trip I was able to produce was only 42 MPG and it was short and predominantly downhill.

Out of concern, I took my car into the dealership where I bought it yesterday and told them to check it out because I wasn't getting the gas mileage that I thought I should be getting and we had smelled an unusual burning odor after driving the car.

Well, after they had it for about 4 hours, the Service Manager called me up and said my car was ready. He told me that nothing was wrong with my car. He said that they had checked all the systems and they were all working correctly. He said the odor is the cadalytic convertor and that it would go away after the car was broken in.

Well, on the way home I decided to fill up the car with the best gas I could get. I stopped at Chevron and filled up with their highest grade Techron fuel. This was my second tank (earlier described 37 MPG).

I reset A&B trip meters, went on my way and nearly got 49MPG on my way home w/heavy wind and storms going uphill most of the way.

I now have run a couple of trips and have achieved 60 MPGs. It is now easy to maintain over 60 MPGs for long distances and even hold it between 80 & 120.

Either the gas made a HUGE difference or my dealer's service department fixed something and lied to me....

:unsure:

Well, whatever it is, I'm glad it's fixed.... kinda strange

 

Hi Tmrpro:

___I don’t know what it was that was killing your mileage but the grade gasoline isn’t it … There is actually more Btu/gallon in lower octane fuels.

___In any case, what ever the problem was, I am glad it is gone. Let us all hope you can begin to enjoy your vehicles benefit instead of wondering what was wrong with it?

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

 

Hi Wayne,

So does this mean that you'll get better MPG with lower octane fuel?

 

Hi Tmrpro:

___Although there are those that will debate Premium vs. Regular unleaded (91 vs. 87) to their deaths, I believe so. The only item you could possibly consider here is if your HCH’s timing were retarded because of knock. I am sure the HCH has a KS (knock sensor). The only time your mileage would be affected under a timing issue is when you are into the accelerator hard and the KS were to pull back your 1.3 L’s timing. You would definitely lose HP and probably lose fuel economy in that instance. Premium has a slower flame front so it will not knock and timing will not retard under just about any condition the engine could be driven in. Someone driving normally or for fuel economy will never have the KS activate to retard timing so I will not waste my hard earned cash on Premium unleaded.

___There is an emission issue with this entire Premium vs. Unleaded discussion as well. In most major cities throughout the US, high sulfur fuel is prevalent. If you have an Amoco/BP near you, their Ultimate (Premium unleaded) is low sulfur and will bring your HCH in line with the California emission ratings. Usually about 1 or 2 levels above those of us that are using high sulfur fuel. In other words, if you are driving the PZEV-AT version of the HCH, you are really driving ~ a ULEV/ULEV-II when using high sulfur fuel. (10 vs. 8 on the EPA’s Green Guide scale). If you are driving the ULEV version of the HCH, you are driving an ~ LEV (7 vs. 6 on the EPA’s Green Guide scale). There is a catch to this as well. First, all fuel will be LS (<30 ppm – low sulfur) by sometime in 2006. Second, you can purchase LS AND low-benzene fuel in non-Premium form from Holiday station’s if you happen to live or drive through MN. or upper WI. using what is called “Blue Planet” fuel. It costs ~ the same as high sulfur regular unleaded with all the benefits of low sulfur in terms of cleaning the air. You live in Nashville, right? If so, you and I will be waiting until 2006

___Good Luck

___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net

 

My HCH went back to the dealership 4 times until they unknowingly fixed it.
I had a problem with the battery level sensing and charging system.

The last time it was there they checked everything over again, called their support center in California, checked databases and reset the IMA computer by reseating some fuses. Then they told me the car was working normally. I asked for a meeting with the regional service manager.

Ever since I drove the car home that day it has worked flawlessly, about a month ago. I even cancelled the svc mgr meeting. They said they didn't fix a thing.
Steve

 

:huh:

That's really scary... hmmmm :unsure:

 

Wayne,

Thanks for the info....but...

I always thought that cars advanced their timing automatically on acceleration.

Didn't older cars have aftermarket advance kits? You know; different weight sizes and spring strengths for different advance stages / RPM range based on centrifugal force...

I've never heard of a KS, but I think the timing must be advanced in order to keep from having the lower octane gas fire prior to intended ignition. This is referred to as pre-ignition or pinging.

It is my understanding that because lower octane gas has a lower firing temp and compression stability, that it would be more apt to burning over a wider timeline of the compression stroke therefore resulting in "less efficiently".

I may be wrong, but I think that's the way I understood how ignition timing affects pinging and the burn cycle of a compression stroke.

 

I've driven my HCH for 22,000 miles now. I experience the exact same thing you did when I first got it, but I never took it in. In fact, my mileage didn't get over 40 until after 2000 miles or so. Between 2K and 20K I've gotten exactly 44.5 mpg (manual calculation - the display is never right). However for some reason now that I've past 20K, I'm up around 46-47 consistently - same commute, same driving conditions. I'm hoping it's a function of break-in and will continue.

Greg

 

Todd,

In the database, are you putting your FCD mpg, or are you putting
down what you calculate at the pump? And if it is calculated, is it
much different than what you're seeing on the FCD?

And you mentioned some high mpg numbers (40 to 60) for a couple
of trips. Did the rest of your driving on the same tank(s) bring the
mpg down?

First, I'd be concerned if there's a big difference between the FCD
and your calculated mileage. The difference is not big, in my case --
about 1 to 2 mpg above or below what I calculate.

If the difference isn't that big with your car, then hopefully you just
have a car that needs more time to break in, as mentioned by Greg.

Hoping you see great improvement soon!
jinno

 

I suspect the break in period had more to do than anything. Even with a regular engine, there is a break in period where the gas mileage is reduced for the first couple of tanks. I've heard the period can be as long as 500 miles.

What happened when you went back to the lower octane?