I currently have a 2009 Toyota Venza with 174,000m on the odometer. V6 AWD
I’ve always been back and forth from 87 octane to 91 octane just to see if there could be a difference between. I have noticed bad idling here and there and below will be what I’ve done to try to diagnose this idling with some of my findings. What I’m trying to answer will also be found below.
Last Monday I filled up a full tank of 87 octane from Circle K. Drove it till the light came on. Prior to filling I added a basic injector cleaner to the tank. During the past week at idling I would notice synchronous vibration like a heartbeat coming from the engine. Just vrr vrr vrr vrr at idle and if I slammed the gas the car would sometimes hesitate.
Fast forward to today, same driving route, same level of stress on the engine. I this time filled up with 91 octane out of curiosity and put in the same injector cleaner. This time I had filled up at chevron. The car idle is extremely consistent. I can’t audibly detect any vrr vrr like before. Slamming the gas is also promptly rewarded each time without hesitation. I even had a little tire slip on these cheap Chinese tires I bought two weeks ago. 🤣
I’ve even timed it before between a tank primarily at 87 or 91 and found the 91 would appear to turn over faster. Honestly tho, I’m not the best with a stopwatch so you can probably ignore that.
These findings have been generally consistent across fuel brands save for buyers bias where I feel like 91 from chevron nets the best results.
My concern is what’s going on in the engine that causes this heartbeat idle I get when I use 87 octane fuel? The car manual says 87 or higher. My injectors are pristine, just had them professionally cleaned 2 weeks ago with the tire job, spark plugs are 1 month old, intake filter is brand new as of 3 months and clean.
The entirety of the internet is naysayers going ooof no benefit. Higher octane me drool on shirt trust me no data to back up hur hur. So this isn’t necessarily about octane ratings.
I’m trying to figure out if my car has something wrong internally that causes a very noticeable and audibly measurable difference. Not to mention the very apparent .5 to 1.5 second delay on slamming the gas and receiving feedback at 87 compared to 91. If I can get ahead of whatever wear or damage has occurred I’m hoping to push this engine past 300,000. Currently an Uber driver if you need my driving style 99% of the time.
The most likely cause is water as opposed to a bad mixture. A lot of fuels come from a few suppliers feeding a number of stations. A high use station is your best bet. Their tanks seem to be cleaner from all the constant refilling. There’s no reason to be torn to pieces over this as it’s not a problem. There’s an automotive TV show called Engine Masters. They test engine parts on an engine dynamometer . They tested a number of fuel grades on the same engine and the results were surprising. Less than a 10 HP gain from regular to high test. Using 87 should not be a problem as ANY engine with electronic ignition will compensate for any differences in fuel octane.