Can I use 87 octane gas in my 1993 Lexus SC300 - manual says use 91 octane?
Question: When I use 87 octane, it works fine withou a knock. am I hurting the engine. I am trying to save $$$>
Best Answers: Can I use 87 octane gas in my 1993 Lexus SC300 - manual says use 91 octane?
It's important to use the recommended fuel for your vehicle. Your spark plugs were made for 91 octane, so they go off evenly with 91 octane. If you are using 87 octane, you might be spending less at the pump, but your spark plugs are not firing evenly with the gas you are using. What you are doing is making your vehicle use more power and getting less outcome. You're also losing fuel efficiency, so you're going to have to fill up more often. You might think you're saving money, but in fact, you're ending up paying more economically.
If you hear pinging that sounds like a mid-pitched rattle coming from the motor when accelerating from a stop, you need a higher octane fuel. I was surprised that my own car runs fine on 87 instead of the required 93 octane. It's a 1998 Grand Prix GTP with headers, cold air intake, a smaller diameter pulley on the supercharger and a stage 1 ECU. After 80,000 miles of 87 octane it still runs great. I have 205,000 miles on the motor and there is no ping even under heavy boost conditions. Surprised me, I've always told customers not to use the lower octane when higher octane is recommended by the factory. Now I tell them to listen for the ping or rattle and let that be the deciding factor. The more octane rating the gas has,the more inhibitors added to stop pre-ignition pinging. Lower octane gas burns better because of the smaller amounts of inhibitors added, so using higher octane gas will not give you more horsepower, it only prevents pre-ignition.
Depending on where you live you may be able to get away with it. Typically if the car requires 91 you can get away with 87 in the winter months, 89 spring and fall and 91 in the summer only. If you're trying to save money an SC300 probably isn't a real great choice though, I can't imagine insurance on one of those is cheap since it's a non turbo Supra with a lexus badge. Also checking your tire pressure regularly and keeping up on oil changes and other maintenance can save you far more in the long run on improved fuel economy.
Of course...there's an old saying...anything is possible !! I believe it would probably end up costing more than the car is worth, lets' say you do the swap, that really has to be part of a much larger plan, otherwise what do you have? a stock lexus with a stick..I have a 2001 GS300 all stock appearance.but with a HKS custom turbo set up..very stealth and actually pretty quick, the whole install cost me under 5K..fairly easy install. I've driven many sc300s' fantastic just the way they are..add the turbo every time you step on the gas you'll get a grin on your face !!
In the long run you will. The reason is that some engines run on the extra high compression. I forgot but some small trucks you are NOT supposed to run on ethyl, being that they are low compression engines. You might save now, but pay later. Here is what you do. 1. Take at least two tankfuls of gas in your car and get an accurate mpg for your vehicle. Then do an oil change but with SYNTHETIC oil. After 1000 miles do a two tankful fillup and get the mpg of your vehicle. If you figure right you will see you are saving money on gas. Also, you do not have to change oil till 6 months. But I tell everyone, change the oil filter at 3 months and just pour what oil you can back. If you go to Walmart they sell the buy 5 qt bottle and pay for 4 quarts. 2, Buy some Plus 4 sparkplugs. They last longer, get a hotter spark so detonate the gas cleaner and better, and therefore giving you just a wee bit more of power. Yes, they run 4 times more than regular plugs, BUT they last as long. And you have to look at the money you save in a year or two. 3. Buy your spark plug wires like at auto zone. Lifetime warranty and change them when you need. Now me, I change the oil ONCE a year but every three or two months I do a quick filter change. I got a 92 Ford Explorer with 230,000 plus and still running good. The only thing I had to change was the power steering unit, power steering lines, and oil pump. Then I noticed a water leak in the water pump, starting so I will change that. My philosophy spend now. Save later. Once you see the money saved with the syn oil, like me, you will just use it for any vehicle knowing you are automatically saving money.
In your situation you should use the gasoline that your manufacturer recommends. Does your friend have a degree in automotive engine engineering? My guess is that your vehicle has a high compression engine or has either a turbocharger or supercharger. This is why a manufacturer would recommend a higher octane fuel. Octane has nothing to do with the amount of energy in the fuel. You do not see any benefit from high octane fuel unless you have a high compression engine. The octane rating is the fuel's resistance to spontaneous combustion under compression. The higher the octane rating, the more compression it takes to make the fuel spontaneously ignite. A high compression engine requires higher octane fuel to prevent detonation. Detonation is a condition where the fuel air mixture ignites while being compressed before the spark plug fires. Detonation can cause serious internal damage to an engine. You can usually hear when detonation is occurring. With the engine under a load or hard acceleration, you will hear a knocking noise coming from the engine compartment. Sometimes this noise can sound like a bunch of marbles rattling around in a tin can under the hood. When you ease up on the throttle this noise goes away. You usually won't hear this knocking noise on a modern computer controlled engines because they have a knock sensor to detect detonation. When detonation is detected, the engine management computer will adjust the fuel / air mixture and ignition timing to stop the detonation and protect the engine. When this happens, there will be a loss of power and fuel economy. By using 87 octane fuel in an engine that requires 91 octane fuel you are at high risk of damaging your engine by this detonation. Usually you wil either burn a valve or burn a hole in the top of a piston. Either can cost thousands of dollars to repair. Sometimes this is not repairable and you must replace the entire engine. So you got to ask yourself which is more cost effective. Spend a couple extra dollars on a tank of fuel. Or spend $5000+ to replace your engine.
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