sha4000

iTrader: (1)

This post for the win. I just did the conversion for speed and your gas mileage will suck all day everyday. Throw in the A/C and it gets worst.

sayow

I admittedly drive like a grandma, but I get 20-21 MPG city and 26-29 on the highway. The OP's numbers do seem awfully low to me.

qha_vn

A/C must be always on in my driving condition: full of dust and noise

peterls

- For Chevron Techron, you need to run it regularly, not just "once, few years back" but every few weeks! (if you gas up once a week on average).

- I cleaned my cooling system by running Preston for three days, only that and distilled water for full three days. After that, when I flushed that out, it was all mud - brown and dirty, so I had to flush it with distilled water, twice, to get it to come out cleaned! Then I put in the new Toyota and ONLY TOYOTA coolant, and it was the biggest difference ever. The reason why it worked in my case, was that our engines have some very small passages for coolant, and if dirt and/or rust accumulates there, coolant does not get in all areas, and your transmission does not get cooled properly leading to friction losses in the transmission and loss of power resutling in bad MPG.

- As for K&N, sorry to say, but that filter is pure junk. I am not just stating an opinion, there are measurements out there, done by pros, and they all show it. The only time K&N works is the first moment you put it in. But because it does not really have much of a filtering to speak of, it gets clogged up quickly, and then it lets even less air than any other cheap air filter. The best filter is OEM, and they are all very, very thick, exact opposite of K&N. The reason they are so thick is that particles get trapped easily, and stay on the surface of the filter, so air still has lots of space to get through to the engine.
In tests, K&N works better for the first few hours, then works much worse than any other filter.

But all of that does not explain your poor MPG...

Here is one thing that I'd do in your place: do an emissions test, even if you don't have to, and see what you get there, what kind of values. They always point to something concrete - you can tell exactly how is your combustion, or if there is too much air, or whatever.

By error, I did my emissions test a few days ago, thinking I would need it for registration, but it came out that I did not need it. Here are my values:

15MPH:

CO2 = 14.8%
O2 = 0.0%
HC = 8 MAX = 71 AVE = 12
CO = 0.01 MAX = 0.38 AVE = 0.02
NO = 6 MAX = 524 AVE = 152

25MPH

CO2 = 14.8%
O2 = 0.0%
HC = 5 MAX = 54 AVE = 11
CO = 0.00 MAX = 0.48 AVE = 0.02
NO = 0 MAX = 481 AVE = 145

Those numbers confirm what I know: my engine is running like new. But if it were not, either HC would be too high, pointing to poor combustion or too much fuel, or perhaps NO would be too high, pointing to too much air...

And then, there is the dreaded compression test - do a compression test, and if your compression on all 8 cylinders is within spec, you are golden. If it is too high, you have carbon deposits, which is the exact situation I had on my old Integra a few years ago. I ran B12 Chemtool in my oil for a few minutes (the engine must be cold for that!) and since then, my compression was within spec (btw, this can easily ruin your seals, so it is a bit risky).
But if your compression is too low, other than a complete rebuild, there is not much you can do.

There is also a possibility of power loss in transmission, or differential... maybe bad shift solenoids, although they should throw a code. Speaking of which - have you checked your codes recently?

Oh, and very easy to miss: your rear tire pressure. I run mine at close to 40psi. I know it sounds too high, but it makes quite a difference in MPG, and it is perfectly fine for driving. Just don't run it high on fronts, or your steering may become twitchy.

Also, your MPG should improve in summer as opposed to winter, especially in Canada.
EDIT: wanted to say that I also cleaned my throttle body, and checked my engine for sludge and such, when I did valve cover seals... you may want to do the same, or at least open up the driver side cover to see how is the engine doing. If the cover is clean, it's all good, but if there is stuff there...

qha_vn

interesting things about K&N, i never knew your story before. anyway, I will leave it there for now.

my purpose of this thread is to get some numbers to compare gas consumption among people driving in similar road condition. but it might not the case when most people here are in US.

AFLS400

I just made a run from Miami Beach to Palm Bay FL on Mobil Premium Unleaded 93 Octane. My MPG was 26.7 at 71 mph on cruise control. I am sure I could average 30 MPG cruising at 55 mph, but I would end up as roadkill driving that slow!!

timmy0tool

iTrader: (7)

actually i think you'll get similar if not less mileage if you go slower. i find that the sweet spot for our cars is above 75mph! it's a combo of air resistance, accelerator input, vehicle weight, and engine condition that contribute other than the road condition itself. also it helps to have that extra 5th overdrive gear, you 98-up owners!

peterls

Just as I was bragging about my car's mpg, I refill yesterday and get 17.5 mpg!
OK, it was all really busy city driving, cold weather, and me being impatient (aggressive), but it was still a surprise.

However, I did fill at a different pump this time, so maybe there was an error there too... Trying to be very careful now, to see if I get a different result.

One thing that I noticed, but couldn't confirm yet, is that this engine seems to be really sensitive to outside temperature and mpg changes accordingly.

Shmee

iTrader: (3)

Again, it's not a simple matter of a constant speed we are talking about. It'll be more like stop and go city driving on the highway for the OP and crippling gridlock for the city.

Again, when I was in SE Asia, driving on the highway was nothing like what we see here.

qha_vn

just for you to have an idea of how everyday drive looks like in HCM :-)



this is what they call "highway" in VN

kevvo

Considering the circumstances of so much traffic your economy now seems reasonable.

AFLS400

You are probably right. I just got 440 miles (338 hwy/102 city) out of my last tank. The low fuel light was on and the trip computer showed 38 miles left to go, but I didn't want to take the chance of running out of fuel. Anyway I will try cruising at 75 mph to see what my MPG numbers show.