sarmyth

Indeed it's not the same! The block may be the same, but the heads and the fuel delivery system are very different.

Camry / RX / ES => 10.8 : 1 compression, no direct injection
GS / IS => 11.8 : 1 compression, direct inject + port injection

Up to a point, the more ignition advance you can run, the longer your power stroke will be == more HP. Said another way, the higher the octane rating of your gas, the earlier you can ignite the charge without it detonating when the piston is at TDC.

We shouldn't have debate there.

Now if you're running lower octane gas, this means you'll run into detonation sooner, which also means your exhaust temperatures will rise sooner.... the sensors will keep you on the edge of detonation which will produce the maximum amount of heat to the exhaust system.

So when normally this level of heat would be at full throttle 6k rpm, you may see this at (make up a number) 3/4 throttle at 4.5k RPM.

So does this marginally impact the durability of your engine/exhaust... sure! If running at 3/4 throttle and 4.5k produces the same amount of pressure and heat as full throttle at 6k RPM then yup.. that sounds like more wear, insignificant wear, unless you're doing this alot, but more wear never-the-less.

Does it matter, probably not.

You're only going to "hurt" your car if you on the track running to redline for hours at a time, you'll end up overheating faster... if you're meandering through traffic or cruising under light load on the highway, it really doesn't matter.


That being said I run premium myself just because the price difference is ~$2 a tank and the extra torque which is spread over the range of engine operation is worth it to me.

sarmyth

I always love watching this discussion. Here's how I see it.

Up to a point the more ignition advance you can run, the longer your power stroke will be == more HP. Said another way, the higher the octane rating of your gas, the earlier you can ignite the charge without it detonating when the piston is at TDC.

We shouldn't have debate there.

Now if you're running lower octane gas, this means you'll run into detonation sooner, which also means your exhaust temperatures will rise sooner.... the sensors will keep you on the edge of detonation which will produce the maximum amount of heat to the exhaust system.

So when normally this level of heat would be at full throttle 6k rpm, you may see this at (make up a number) 3/4 throttle at 4.5k RPM.

So does this marginally impact the durability of your engine/exhaust... sure! If running at 3/4 throttle and 4.5k produces the same amount of pressure and heat as full throttle at 6k RPM then yup.. that sounds like more wear, insignificant wear, unless you're doing this alot, but more wear never-the-less.

Does it matter, probably not.

You're only going to "hurt" your car if you on the track running to redline for hours at a time, you'll end up overheating faster... if you're meandering through traffic or cruising under light load on the highway, it really doesn't matter.

That being said I run premium myself just because the price difference is ~$2 a tank and the extra torque which will be spread over the range of engine operation is worth it to me.

sarmyth

Premium doesn't burn "cleaner" it burns with more stability (with regard to pressure ) and slower =)

Nismo

Personal memories last the longest, and I once broke a big chunk off of a piston due to detonation caused by not running the correct octane fuel that the engine required.

I don't trust anti-knock sensors to always works, so I always run premium in the GS.

For those that don't, you can get away with it in a modern engine so long as your anti-knock sensor(s)' never fail. It'll also be less of an issue in the winter, due to the colder charge being less likely to pre-ignite than a hotter air charge in the summer.

scham21

Considering your in a $50k+ car i dont see why you would even consider not using premium gas. If you cant spare the extra 4$ a fill up maybe you have purchased the wrong vehicle.

Joeb427

iTrader: (1)

Afrosheen

Amen to this. It's always premium for me, 91 or 93. Texas gas.

Infamous3

Yeah but that $4 adds up. You could save a lot of money by using regular lets say for a year or two. All depends on how much you drive. And thats not really saying much, normally 50k cars are in the 2k down/500 monthly range if you lease, thats not a whole lot for a working adult.

Me personally I don't use regular. I have a lot of friends with leased cars who require 91 but they use regular because its a lease and they don't care. I used costo 91 gas once and the drive wasn't nearly the same nor was the performance. If the difference was that significant with costcos cheap 91 gas I can only imagine how significant the switch from 91 to regular must be

rominl

iTrader: (4)

typical say 15k miles a year. say the car avg 23mpg, that's 652 gallons. between regular and premium, say 30 cents difference? that's less than 200 bucks difference, which assume 600 buck lease (0 down), that's 1/3 of a month's payment per year.

so imho, still, if anyone has to worry about that 200 bucks, the person got the wrong car.

but of course, from a technical point of view, i welcome this discussion and i always think it's an interesting one (it's always a debate basically). but from a practical point of view i never think it makes sense for the difference

sirsaula

Days I feel cheap I use regular but 98% time i use premium...who cares..if engine can take it do it...everyone else here can go blow one. IMO

ECL

For the past 20 years, i have run my SC400 on regular gas. At $200 per year, that adds up to someing like $4K. The SC continues to run great. YMMD or YMMV.

rominl

iTrader: (4)

4k over 20 yrs, sorry but that's still nothing compared to the price of a premium luxury car no matter how you slice it. i am not saying 4k is nothing (just like i am not saying 200 bucks a year is nothing), but it doesn't change the analogy.

scham21

Leasing, buying, renting whatever. Whatever it calls for is what you should put in it. its a privilege to drive a lexus

scham21

Yea ive done a test in my older gs putting in regular for a month and the car didnt drive the same and the gas mileage went down. So yes the engine could be ok but then again you probe cancel out your savings from the loss in gas mileage. Try the premium for a month and see how you like it.

scham21

You can do 0$ down and 600$ a month leaseing a GS?? For how long??