i've been stressed with todays gas prices and decided to start using regular unleaded fuel instead of premium. i havent really notice much of a difference. since the owners manual says premium only, do you think this could hurt my engine? and alternitives?
thanks, movaaa.



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99' silver Gs300 stock.

 

you car will slowly get weaker if you keep pumping regular

 

Short term alternative: No.

Long term: Yes

 

It will not hurt your car. You wont get the performance that you should being the timing is set up for 91 octane. You will get what I beleive is called early detination, where the fuel ignites before it is supposed to causing slight knock that you cant hear, but the knock sensor will. It will then retard your timing to adjust itself to the lower grade gas. So as long as you dont care to lose some power and i would say it is minor at best then it is perfectly fine. For normal cruising you wont know a difference.

 

If you normally cruise slow then it should be no problem. This engine is pretty tough. Just don't take it past 4000rpm too often. Try to stay under 3500rpm if you can. You will lose a bit of power, but since you aren't going to floor it then it won't matter. I've used regular in my highly tuned engine a few times on long road trips because I knew I was just going to be cruising on the highway at 2500rpm. No point to waste that extra money. Only real problem was fighting the urge to gun it on long open stretches and when someone on the road wanted to mess with me

 

Is this true that the GS300 (2JZ-GE) is tuned for 91 octane? I was under the impression that is was tuned for 95 RON? If it is 91 RON then unleaded here I come - when I eventually get a GS300.

 

As gas prices increase, I think it's more of a reason to use Premium rather then regular, as the % increase is less.

So say Premium used to be 20% more expensive, you definitely didn't get 20% more MPG or performance.

But now as gas increases, Premium is maybe now only 5% more expensive then regular, so it is more of an debate if the MPG or performance increase from the proper octane would cancel out the price increase.

It's easy to notice the couple of dollars you saved while pumping, but it's way harder to notice if your miles/tank dropped for example from 210 to 200miles (5%) or might have even been more-actually causing you to lose money by switching to regular.

 

Run whatever you want. I have always run regular 87 in my car and have not had any problems. I agree with JeffTsai that you should not push your vehicle unless needed.

 

once my dad put 87 in the tank and i freaked. the car felt really sluggish.

 

Is everyone talking about GS300's? I've always run 87 in my 300. I was unaware if it should have been 93 octane. I could see the GS 400's taking the 93 octane. Can someone clarify this?

 

I don't believe it matters that much. Compression ratios are similar and that is what determines the octane requirements.

 

What's the gas prices like around your area? For me it would be $2.99 regular $3.29 Premium. So lets say I take 16 gallons on a fill up, it would be $47.84 w/regular gas and $52.64 w/premium. So, if my first grade math serves me right, that is a difference of $4.80 per fill up. My point, why risk damaging or lowering the performance of your car/engine for $5? I know it adds up, obviously, but if you can't stand the gas prices that bad, like most of us.... Get yourself a 4 banger.
I hope I didn't sound like an a-hole. But just my $.02

 

It doesn't really mess anything up. You just lose performance. BUT...if you're just cruising like a granny then why does it matter? I use regular when I go on road trips because I know I'll be keeping the car at a constant 2500rpm or so.

 

I have been putting premium for 2 years, after this tank is empty ill try regular and see what happens

 

I think there are a couple issues here and they are all separate.

1) Engine wear/Damage
2) Performance
3) Actual savings (Miles per $)

The first 2 issues probably probably don't hold up very well as pros for premium.
1) You're probably not going to damage your engine
2) You will have less performance, but doesn't matter for the penny-pincher.

3) Here is the most interesting point to me. This is probably somewhat related to (2), but I believe the engine is designed with Premium in mind, using Regular will result in some worse efficiencies. It's clear this affects peformance, but I believe this also leads to subtlely worse MPG (but is hard to really observe). So whatever savings you thought you had, would be canceled out.