Can I just change grades of gasoline?

tonfada

I am NOT a mechanic by any means, so please stay with me.
Since day 1, I have been feeding my Toyota Corolla (in the year of 1999, and I bought the brand new one.) with super gasoline (93), and I didn't realize that the car only needed regular gasoline (89) to run until last week. To save money on the gasoline, can I just switch the gasoline from 93 to 89? Or is it ok to switch it to regular gasoline? If ok, what do I have to do particularly to avoid any problems? Please let me know... Thank you.

James

Mr_Shiftright

Actually 89 octane is not "regular", it is often marketed as some type of mid-grade. Most regular I've come in contact with, on the West coast anyway, is 87 octane, which may not be enough for your car.

But sure, just put in what the manufacturer says, no problem, and save yourself some money, too.

zueslewis

check your owner's manual and follow the recommendation. Using anything but what is recommended does nothing for your car, only deflates your wallet.

arkainzeye

i have the same car as you.. i have only used 87 octane. When i was in college i had a instructor that told me a story about his brother going to Penn State for chemical Engineering. and they had a lab project on gasoline. To make a long story extremely short. there was no real difference in the higher grade gasoline. Now if you have a high compression engine. "which you dont" then i could maybe see using 93-94 Octane. but other than that you'r just wasting money. i used high octane in my corolla and seen no difference in proformance. and the same thing went for my chevy tracker, ford rangers etc etc/
now if i maybe had a sports car, then i guess i may see a difference.

zueslewis

your ECM can't "read" any difference in octane, so no performance differences are seen. On a Corvette, for instance, 91 octane is required - if you use 87, it will run like junk. The ECM senses worse octane, not better, through several sensors.

britton2

have a '01 Corolla - sometimes I put in 89 octane as opposed to 87 - I get about 2 more MPG using the 89 -

zueslewis

conditions contributing to your increased mileage - the octane difference is not capable of making that change - I mean no offense. There are many factors that effect gas mileage.

shipo

Unless your car has an upgraded ECM, it is more likely that you will see worse mileage with 89 than with 87. Also, unless an engine has either enough compression (the Corolla does not) to cause a hot enough burn, or the ECM is capable of firing the plugs early (unlikely, unless you changed your ECM), your engine will likely develop extra deposits in the combustion chamber and on the valve stems.

No matter how you slice it, you are better off using 87.

Best Regards,
Shipo

zueslewis

that "richer" fuel causes more gunk collection - bummer.

Weird question - I have an '88 Suzuki GSX-R 750 with a Keihin Flatside carb conversion, Yoshimura Carbon Fiber Duplex Exhaust, etc. Am I right by running the highest octane I can get? It's not injected and has no ECM, so wouldn't better fuel make a difference, quite contrary to injected and emissions controlled cars?

krzyss

to find compression ratio for 1.8 VVT-i 130 HP engine in Corolla and I can't. Toyota does not believe that it is important information.
I suspect that it is high compression engine and using higher octane fuel gives you better milage.

Krzys

PS Manufacturers often say that engine requires regular gas but HP numbers are obtained using higher grade. Of course ECM (the computer, which controls engine) must be able to utilize higher grade.

PS2 Yes you can use the lowest suggested octane any time you want and if it is not available you can use higher or lower (I would suggest higher ;-). ECMs are quite clever nowadays.

zueslewis

I doubt the compression ratio on a stock Corolla is higher than 9.0:1. A Chilton's or Mitchell's Guide would say for sure.

zr2rando

of money.
A high compression engine benefits from high octane, normal engines will have no benefit from it. I have always noticed worse gas mileage when using high octane in normal comp-ratio engines.
Very low octane gas can cause knocking in an engine and a modern ECM will adjust spark timing to compensate for it, you would want the cheapest gas that does not knock (your ECM can only make so much timing change..)
If your book calls for 89 then try to find 89 and if you can't find it use the 87 , only use the 93 if the knocking is constant. Typically the ECM will keep the timing advanced as much as possible and you will hear a slight knock every now and then which is ok, constant knock will happen if the gas is just way too low on octane rating.
The lower octane gives less carbon buildup like several folks have already stated,,,,save yourself some money, and help clean up deposits while you're doing it,,,,gas isn't getting any cheaper at the moment...

britton2

that's OK - I take no offense at your comments - and I am the first to admit that I don't know anything about ECMs and the like - all I know is that I check my mileage at every fillup - and using 89 octane gas gives me better mileage than 87 - I haven't used 93 and don't plan to (around here it's 87, 89 or 93)

mpyne

I also have a corolla and was i have been using 89 octane for around 8 months. i read about the higher octane causing carbon deposits. My question is if i switch back to 87 will these be cleaned out of my engine? Also does this cause any long term damage??
thanks

zueslewis

will not be cleaned out by using 87, but they will not be contributed to further. You must perform a top end cleaning service (transmission fluid works wonders, smokes like crazy) in order to clean the deposits.

opera_house_wk

Put it in the gas? Squirt it in the intake when it is running? Like they used to do with water. Or squirt it in the spark plug holes and let it sit overnight? I've done that to clean up rings.

zueslewis

has the highest detergent quality of most any fluid/lubrication. The easist way to use it is to disconnect a vacuum line, insert it in the bottle of tranny fluid, and let it suck it into the intake. The trans fluid burns and cooks the crud off of everything -

It will trash the spark plugs that are in the engine now, so get a fresh set for after the cleaning process. Also, have a buddy or significant other manipulate the throttle - your engine doesn't like burning trans fluid and it'll smoke like crazy and try to die.

Revenge tip #1 - aim your car's exhaust towards the neighbor you don't like.

pjksr

These 2 brands of high-octane advertise thier higher detergencies, compared to 87- and 89-octane grades ("drive your engine clean."). So, is this higher level of detergency, in fact, made necessary because of the fact higher octane levels cause deposits? The advertising makes it sound like the detergents are a bonus (or "plus") that you get for buying high-test!

swschrad

but burning higher octane than the engine is designed for will leave lots of carbon deposits in the cylinder passages. so they NEED to put more detergent in there so the schmucks who get taken by the "87 octane good, 93 octane better" argument don't spread stories in a couple months about how Stinkmaster SuperPremiumWithBleach turned their car into a limping dog that cost $300 to fix.

alcan

What are "cylinder passages"?

qwertop

the 99+ corolla has 10:1 compression ratio. I think toyota still recommends 87 octane though.