It has to be that on my 1994 GS 300. It is drinking gas.

 

2003 RX300, 109K miles. 15-17 in the city, 18-21 highway. Overall average is never more than 20 mpg. Engine and vehicle well cared for now, but the original order didn't do a very good job with that.

 

Hyper-miled on a highway trip. 70-90 mph for most of this. About 70 miles traveled, net elevation loss of about 500 feet. I didn't hit the brakes a single time for the first 65 miles.

I refilled the tank when I got back to audit the computer and it's accurate.

Around town I get 17-22mpg depending on the city\highway balance.

How is this possible?

 

slow elevation loss and favorable wind can make a lot of difference I guess; very good to keep the momentum

 

1995 got 26mpg over 732km on a tank of Sunoco premium 93 driving from NJ to Toronto, after a fresh oil, trans fluid and coolant.

Usually get mixed city highway on Petro Canada 92 of 17-19 mpg.

 

22 MILES PER GALLON ARE 20 KILOMETERS PER LITER. THIS IS SPECTACULAR, INCREDIBLE, EXCEPTIONAL. At what speed do you get this? Always on flat roads, with no ups and downs? In which state do you drive this car and on which roads? thank you very much.

 

1999 LS 400, stock everything, 235000 miles. Burns nothing but regular gas, tried premium and mid grades no change. Mileage is verified by Garmin GPS. Odometer records approx. 1-2% above actual, Speedometer is 3-4 mph faster than actual. I record every gallon in and the mileage as corrected by GPS.. Solid 21-22 commuting, on the Hiway going to WI from NC the average was 24-25 every tank, freeway speeds 70 MPH +.

Vehicle miles per gallon on the computer is normally 2-3 MPG higher than actual.

Miles driven on a tank means nothing, the gauges are not any more accurate than the speedo. I don't favor one brand over another, it is the price per gallon that makes me fill up.
Car has only had the normal maintenance performed, original stock muffler.

 

You have been using 87 octane with no issues?

 

Lexus recommends "premium" fuel only....

Premium for 1969 GTO was 100 octane.

91 octane for 10.5 .compression Lexus is probably as low as you want to go.

ECU will compensate for 87 octane fuel by retarding ignition and enriching fuel mixture...not sure whether transmission upshifts delayed..

Perhaps computer program tabulates MPG based on using 91 octane fuel?..so.the computer readings display higher MPG than actual when you used 87 octane fuel vs 91...

Using 93 octane on 1999, mileage is slightly higher than the computer reading. I routinely see 30 MPG highway mileage. My intake manifold is extrude honed, and Ruthenium spark plugs,.

87 octane = reduced MPG, increased engine wear, and increased carbon build up.in cyliner head, intake runners/ throttle body.

 

I did a mileage test this weekend in my 1999, about 120miles round trip on highway 25 in south Georgia. Returning back home the computer told me i was at 25.7mpg. Running between 65-70mph. This is also with p0430.

 

Interesting that some 400's are not as picky with gas. I've tried multiple times to run varying grades to see and each time the drop in octane corresponds to a drop in MPG and the feel of how it picks up when on the gas. This last time was using Costco Premium and Shell V Power. Shell consistently yields about 25.2 MPG on a flat highway run to San Diego when traffic is moving. Costco returns about 24.4 MPG. Chevron, 76, Mobil/Exxon hover in the 23-24 MPG range. Regular drops ours into the 20 MPG range.

 

I've never noticed a difference in MPG when using different brands of gas in any car.

 

Buddy's with premium calibrated cars comment they see similar drops with changes in gas. When they got to CA for the 2018 Porsche Cars North America Renn meet they reported pretty bad MPG since ethanol fuels are the majority. In the late 90's when there were gas stations that didn't have ethanol infused fuels the LS would get about a 5-8% increase. These days the LS drives like it did in past days on mid grade without the ethanol. YMMV, these have been my observations with ours.

 

As I posted earlier. I have ran the tests with 91 & 93 octane, no change in MPG. I do not use the computer for any mileage readings, It is actual miles driven as verified by GPS and gallons used. The speedometer is off by more than 3 mph, the Odometer is within 2% of actual miles. Throttle body was cleaned, at 140,000 no issues, plugs were changed to iridium no changes in perfomance or MPG. I bought the car as a third owner, I don't know what gas the first owner used. The second owner, drove 100,000 miles on regular gas. I have driven over 100,000 miles on 98% regular, I only used premium and mid grade as a test to see if there was any improvement in mileage or power, none were noted. I have tried a couple of tanks of 100LL aviation fuel, no changes we're noted. I have a couple of friends that are engineers in the oil business and they don't really support the octane ratings. If the engine does not have a knock it will normally adjust the octane. This engine is used in countries where there is no 93 octane available?

 

I get best gas mileage with 91 octane 19.5 mpg

99 ls 400
135k
Bought it used have no idea how it was maintained.

New dunlop tires from wall mart 58$ installed. Lol

32psi all the way around.

Suburb,city and highway. I drive pretty laid back the vast majority of the time but I will open it up from time to time.
Haven`t taken it on a long highway trip yet but I can't wait to see what it gets.

These cheap tires ride pretty nice! At that price I `ll put new ones on every year once tires are half tread they ride like ****!