I do suggest that you get an owner's manual. (A lot of questions here on Y!Answers could be answered if owners just read this book!) You could check on eBay or search for online companies that collect owner's manuals, or call local junkyards to see if they have an owner's manual in the glovebox of one of their wrecks. Otherwise, you could order it direct from the Toyota Materials Distribution Center for $15.95 through
http://smg.toyotapartsandservice.com...py=2003&pubno= , or order it from your favorite discount Toyota parts source. If you have a US credit card, a sufficiently fast internet connection, and a lot of patience to download a bunch of tiny PDF files, you can get a brief subscription ($10 for one day) to
http://techinfo.toyota.com/ and download the 2003 US Corolla's Owner's Manual, as well as many other publications (such as repair manuals, electrical wiring diagrams, new car features manual, TSBs, etc.).
Octane is rated differently in different countries... The US uses the (R+M)/2 method, where "regular" is usually 87 octane, and all gasoline is unleaded for air/water quality reasons. Other countries may use just RON (higher than the US method), while some use MON.
I recommend reading the US Federal Trade Commission's Facts for Consumers - "The Low-Down on High Octane Gasoline"
http://www.ftc.gov/bcp/edu/pubs/cons...tos/aut12.shtm
You should use whatever grade/octane the owner's manual recommends.
http://www.toyota.com/help/faq-service.html
"What is the minimum octane rating gasoline that I should use in my vehicle?"
Current model year US Toyota Corollas use 87 octane.
http://www.fueleconomy.gov/feg/bymod..._Corolla.shtml
shows that all US 2003 Toyota Corollas use Regular (87 octane) gasoline.
If your car is experiencing engine knock (or pinging), then you should go up a grade in octane. (But if your car IS knocking, something may be wrong with it and it may need a tune-up!)
Octane is a measure of the fuel's ability to resist pre-detonation (or engine knock).
Higher octane gasoline doesn't mean that it is necessarily cleaner or better. "Premium" is a mis-nomer. All gasoline sold in the US must meet certain federal EPA clean-burning guidelines. However, some individual brands _may_ decide to put some extra cleaners or extra refining in their higher-octane fuel (as I've heard of some brands advertising low-sulfur gasoline as only in their Premium line).
A higher octane gasoline actually has lower BTUs (energy content) than a lower octane gasoline, so the only way that you'd see better fuel economy by going up in octane is if you were previously using lower than recommended octane in your car...
For an occasional tank, you could get away with using a lower octane than recommended in a car that requires "premium" fuel, as the car will adjust, but it can cause some extra wear on the engine while knocking, besides the lowered fuel economy. (long term use can cause additional engine wear/damage)
If you live in a high altitude area (like the Rocky Mountains) usually you can use the next octane level down from what is listed in the owner's manual because of the altitude/thin air with no ill effects (except if you come down from the altitude with a full tank!).
For some cars, such as the Toyota Prius, using higher than the recommended octane fuel is known to cause check engine lights with engine misfire codes (because of the Atkinson cycle engine, rather than the Otto cycle engine most other cars use) due to the late detonation, besides the expected lower fuel economy.
Reasons to use higher octane fuel:
1. Your owners manual calls for it
2. Your engine is knocking
3. It's the only way to get low-sulfur fuel in your area (sulfur will slowly poison your catalyst, making emissions worse over time)
4. You like spending extra money on gasoline
See also:
Premium vs. Regular:
http://cartalk.com/content/features/premium/
If you don't have an aversion to using either Mobil or Walmart or any other gasoline distributor for their business practices, then go to whichever you like for price/service/convienence... It is possible that they could get their gasoline from the same place, or that one place has better cleaning agents added to their fuel as opposed to another. Some people prefer Top Tier gasoline retailers.
http://www.toptiergas.com/index.html But the main thing is to use the recommended octane of gasoline in your owner's manual...
I also like the History Channel's show "Modern Marvels," the episode titled "Gasoline" for more information...
2003 corolla S perfer to use which kind of gas?
Linear Mode
