Noticing the very high compression ratio of the Camry 3.5L V6, I asked Toyota how they could use the specified regular fuel. Toyota confirmed to me that the stated performance will not be achieved with regular fuel. I've read of engine damage resulting from excessive use of too low an octane fuel. A knock must occur before the timing is changed.
These days engine computers and sensors adjust things to match lower but acceptable octane. You give up performance but the engine is not damaged.
Any instance of knock can cause damage. The minute amount that is required for the ECU to de-tune itself will do no harm - theyre very sensitive and very fast. I wouldnt want it to work in closed loop and be contsntaly trying to change back though -that would worry me - but then i dont have millions of dollars in research to determine how much damage would be done, unlike our favourite auto maker.
Even if you use premium fuel, the PCM will advance the timing until knock is detected. There is really no difference except for the final timing adjustmet point. If the manufacturer allows the use of regular fuel, don't worry. I have had vehciels that specifically stated to use only premium fuel. Even for such vehicles, it is likely that regular fuel will not cause engine damage.
Occasional spark knock will not destroy your engine. Continuous knock can, but the PCM will prevent this.
Ed
Couple of points:
a) the PCM will not advance outside of set limits, it just has a marginal % of trim available to it - thats part of the control algorithm - it has upper bounds which were set conservatively on premium fuel at the research stage. I know of no current PCM units that run closed loop boundless advance. b) Trust me - ive seen "premium fuel only" toyota engines (JDM imports) with mashed piston ringlands due to running normal fuel. I wouldnt recommend it to anyone with a PFO car.
Although most people dont want to believe it, the manufacturer recommends things for a reason. Anything you do outside of that WILL shorten its life, its just your call how much you care.
I think both our Toy's state (3.5 & 3.0) that higher octane gasoline will improve performance but 87 is okay.
If you are a mild driver, don't have to accelerate fast or climb steep inclines regular should be OK. If you are a balls to the wall type driver pay extra and go for it. The difference in fuel costs over the life of the car can be substantial. The cost of engine repair is also substantial if engine knocking occurs. I've gotten tanks of regular gas that knocked and then bought regular gas at the same place later and it didn't knock. My theory, if brake pads last 100K miles you probably don't need high test gasoline.
High octane fuel (all fuel i think to some extent) degrades over time
- if you go to a rarely-filled filling station you may get significantly lower octane than you pay for.
On the costs over time issue - my car more than makes up the cost of v- power (99 RON UK) in magically getting more mpg ! I like it!
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.