Finkler

I know this is a touchy subject for some, so try not to get peed-off…


I’m in month 2 of a 36 month lease. Love the car! However, the gas mileage is horrible… I have 1500 miles on the car, and I’ve been averaging about 17 mpg thus far. 50/50 highway to city driving. Of course I let the horses loose once in a while, but not constantly. Upgraded to a 3GS from a ‘03 Acura 3.2 CL Type-S 6spd, used to avg 24mpg on the Acura, same driving style.

Will mpg improve when engine breaks in fully?

Does anybody have any experience filling up with less then premium fuel? (I’m leasing, so don’t care about the long term effects) Performance, gas mileage difference?

ek9vboi

iTrader: (3)

It should have been broken in already.

If you filling up that car with less then the recommended octane then thats your answer. Our cars are designed on premium gas, not the cheap ****. I average 20mph easily and that is mostly city driving.

Lower octane = lower miles. You have a few bucks, but you lose a few miles. In your case, you prolly paid about 4-5 bucks less on gas for the cheapest **** possible and with that you lose 45 mpg. NOT to mention what that low octane will do to the car over time of constantly using that gas.

I feel bad for the next owner. This is why I wouldn't buy a leased car or used for. If you can't afford the gas, don't buy the car. Should have thought about it before you bought the car.

whlkev

I drive mixed highway and local, and on a v8 with 800 miles on it, i avg 22.7-23.2.

either you drive really aggressive and not know it or something is seriously wrong, i don't see why yours would be so low.

but then again, i don't have this "leased" car mentality and I baby my car.

please don't put lower than recommendation octane gas just to save 3-5 bucks. You drive a car that's worth 50k, treat it like one.

EyeKutr

iTrader: (5)

Gas mileage has soooo much to do with habits and where you drive. My GS300 has consistently gotten me 18 mpg on my commute to work and back which is only like 7 miles each way, stop and go, huge hill to climb in the middle. The times I drive mostly on hwy, i easily average 23-25 mpg for the tank. Just use premium, it costs like 7% more, you will get than in performance and mileage....

Finkler

I’ve been filling up with Premium only… That’s why I’m concerned about my avg mpg.

Could the AWD system account for 5+ mpg? The newly updated, more stringent EPA rating on the car is 18-24mpgs.

I don’t drive in the sport mode, can’t even imagine what that would do to gas consumption.

Ek9vboi – I agree with you about buying leased cars... I just wanted to ask if anybody has seen a difference in performance and gas mileage by using cheap fuel, and if they can quantify it.

I agree, the $3-$5 difference per fill-up is not a big deal I don’t drive enough to make it worth while, I’m just wondering if the car should be tuned/adjusted…

EyeKutr

iTrader: (5)

You know, if you drive about 65 mph on a flat highway, you should see what your mileage is, should be around 28-32 per onboard pc, all other conditions have too many variables. i would love the gs460 to do my route back and forth and see what the mileage is, probably 15 mpg....even my 4cyl camry was only 23 ish on my route

whlkev

on a typical engine, using a low octane fuel will cause the engine to knock, but with advanced engine that we have, to avoid this, the ECU will automatic adjust the engine to adapt to prevent damages to the engine thus reduce the overall power.

2008 AWD can do 18-25mpg, 460 can do 17-24mpg, can't be that bad on your commute (EyeKutr)

EyeKutr

iTrader: (5)

I am willing to bet the farm the 460 will not avg 17 mpg on my commute If you are around Riverside area let me know we can test it out, Ill buy lunch...

cmn

you should not be getting 17mpg. I use regular unleaded in Colorado (i.e. 85 octane because we are at altitude) and get no knocking. I get about 22mpg overall, never goes below 20mpg on a tank, even with all city driving. That's with regular unleaded. When I first got the car I used premium, maybe got 1 mpg more at best, although hard to tell. I saw no performance difference between the two grades of gasoline. I find it hard to believe that without knocking, the regular will damage the engine. and I get no knocking with regular. If you are only getting 17mpg, I would suggest you have a problem unless you are stomping on it. One of the other guys suggestions was good. Fill up the tank and take it on a long highway trip with the cruise control on about 65 mph. If you don't get better than 22mpg on the computer than something is wrong. Also, if you are relying on the computer calculation of mpg, you might want to make a manual check. fill it up and keep track of the gallons you put in and the miles driven over 2 weeks or so and then do your own calculation and check it with the computer's numbers over the same period. I did that and I found that the computer underestimates the mileage by about 1 mpg. yours may be worse than that which would also warrant a visit to the dealer.

spwolf

my average is 13.8...

Why? because my "commute" consists of driving 1 mile, through 7 traffic lights. Local roads I get 30+ mpg.

There is nothing wrong with your car, mpg varies based on your driving condition - you have heavy, V6 AWD vehicle with 306hp. It is not going to be good in the city even if it has state of the art engine and gets better mpg than competition...

tjp74

Like mentioned earlier in the thread, there won't be any damage to the engine by using lower than recommended grade in a modern engine. That is what the knock sensor is for which will detect the knocking/pinging in a split second and tell the ECU to retard the ignition to avoid any damange. That's why you don't hear any knocking noise thus no damage. And performance difference is minimar at normal drive. However due to high compression ratio in direct injection engine used in GS350 and GS460, using premium grade is a must I believe. As compression ratio increase, chance of knocking increases.

sonikbo0m

07 350AWD and average around 18mpg. Highway average around 22-23mpg. The car is at 13k now, so I don't think breaking in the engine is the problem. I'm thinking it's the AWD factor. I baby my car too, driving like grandma. So needless to say, I was disappointed with the mpg.

RacerX1166

First off, the reason that higher octane fuel is required in our cars is because of the 11+:1 compression ratio. The higher the octane level, the more resistant it is to detonation (fuel mixture igniting prior to the spark plug firing). This is because it takes more heat to ignite higher octane fuel than it does lower octane fuel.

You won't cause damage to the car by using lower grade fuel. As noted above, the ECU makes the appropriate adjustments to retard spark in order to insure that knocking/detonation does not occur. As a result, it may lower your fuel efficiency since the car is not running at optimum levels.

If you are going to experiment with lower grade fuel, this is the perfect time of year to do it. The colder intake air helps mitigate the risk of detonation through the use of lower octane fuel.

I would benchmark your current mpg, then try a few tanks of the lower octane and re-check your mpg. Then, you'll know for sure. However, during the summer months, I would not consider using anything but the recommended premium fuel.

Trust me that I'm in the same boat as you with the fuel economy on this car. I thought, when I went from my BMW 540 to my GS350 that I'd get a bit better mileage (which I do but not much) but would save some more money not having to burn super. You can imagine my chagrin when I opened the fuel door and saw that 'use premium unleaded' decal.

The G Man

Have anyone try using the mid grade gas 87 octane, I wonder if the MPG or the HP will go down. BTW, I have a similar commute as some of you guys. 5 miles to work each way, all city. I get about 17 MPG according the on board computer. Is the GS on board computer same as all other Lexus that it actually reads 1 or 2 MPG higher than it actually is. Did anyone here actually try to calculate the MPG manually and compare it to the on board MPG computer?

whlkev

seriously.. up until this day, i do not understand why people use lower than recommended octane rating to save a few bucks at the most?

I would put 95 octane if it's available.

it's already bad enough they went from 92 to 91 and now all gas are blended with MTBE to reduce emission thus reduce its full performance.

Have you tried a mixture of 100 oct race gas and 91? once you go that, you'll realize how much good gas make a difference.

just because it's not knocking (ECU is kicking in to prevent damage) does not mean it won't have a long term effect down the road.