My wife has a 2018 Nissan Maxima 3.5. The owners manual states hi test gas but she always puts in regular. I don't drive or fill her car up very often but when I do I've always put in hi test ..... except for today - I balked at the 54¢ increase in price per gallon and filled it with mid grade instead. I've not noticed any difference in how it runs no matter what grade of gas is in it.
thoughts ??

 

Most vehicles today have "knock sensors" in the engine that determine if the engine is knocking or pinging due to lower octane gas. If the engine detects that it's knocking, it retards the timing until the knocking stops. You'll lose a little performance and fuel mileage, but it shouldn't damage the engine.

 

Thanks Bob, good to know.

 

Higher octane fuel is specified for power. To meet the power output the manufacturer advertises you need to use that octane fuel. Use a lower octane fuel and the computer will adjust but you'll loose a slight bit of power.

 

In a 3.5L I doubt it will even be noticeable. I would do a trial and run the regular for a few fill-ups (need more than one because you'll have some premium still in it). Post back what you find, I would be interested in how it goes. At .54 a gallon difference I could put up with a little less performance.

 

Wife had a Mitsubishi Eclipse Spyder convertible with a high output 24 valve engine. On regular gas, it ran like garbage. On premium it purred like a kitten. When gas got really expensive, went an started to put regular in and then added octane booster to get it to where it needed. We sold the car a year and a half ago and still have 2 bottles of octane booster in my garage. On performance engines it really makes a difference.

 

Her car seems to run fine on regular. I seldom drive her car and probably only put gas in it every couple of months. I had been putting in hi test when I filled it up but yesterday I got sticker shock She thinks her car has plenty of power and her right foot weighs a lot more than mine

 

Wife drives her RX350 for long time now on regular gas.
it does show a bit less of power but again, it's a 3.5 V6 so that's not noticeable at all. Ironically, hers is 2011, they changed spec for SAME engine to regular gas starting 2012. Sales must have dropped, so they "wiggled" that spec....

 

I used to do a lot of long distance driving in my car and kept pretty accurate records of my fuel use. W/ premium I got about 27mpg, w/regular I got about 24. This is over the span of a couple of years. The only difference was the gas. Car ran smoothly on both.

What Bob said....

 

Modern intake/exhaust computers are capable of making adjustments in basically real time, so you have MUCH more wiggle room to trade dollars for octane rating.

 

Premium is the "recommended" fuel for the 3.5L, so as long as it doesn't say "Premium required" there shouldn't be a problem. If the engine is direct injected, that's a second-motion toward regular unleaded being fine. My 08 CTS 3.6L direct injected (DI) V6 is 300 hp and 274 lb/ft rated for 87 octane with no mention of premium, although when using premium, the idiosyncrasies that often accompany cold start on regular unleaded, are less frequent to absent on premium.

Perhaps the 3.5L is port injected, since it has a compression ratio of 10.6:1 and a premium recommendation, given my CTS has a compression ratio of 11.3:1. The 3.6L in its latest edition is now up to 335 hp while retaining the regular unleaded recommendation.

Direct injection is a game changer making it possible to run higher compression ratios without having to increase fuel octane rating.

I have run a fuel economy test over a pretty stable 75 mile distance one way, round trip with no stop in the middle of the stretch, all interstate, exit to exit. I've noticed so far the greatest variation in hwy fuel economy is when I've moved from 89 octane with 10% ethanol, to 89 octane ethanol free gas, which delivered a roughly 2 mpg/hwy improvement, from 30 to 32, according to the console display.

The best achieved on premium prior to testing with 89 octane was 30 mpg/hwy, but that was before the intake valves were cleaned, after which economy improved. At this point, the reduced energy content of the typical 87-89 E10, is not enough to justify the cost increase of ethanol free 89 octane which is probably most beneficial to the few older cars and lawn and garden equipment running carburetors.

If you don't use the same filling station consistently, fuel quality can and will very likely have more to do with performance than octane rating, especially as the seasons change. Some vehicles are programmed to test the fuel grade in order to increase performance as was mentioned in an earlier post.

 

Take a look here,, https://www.jackingramnissan.com/blo...-premium-fuel/ says:
"...the manual recommends using a premium unleaded gasoline with an octane rating of at least 91 AKI (Anti-Knock Index). However, this is only a suggestion and not a requirement.

The manual also states that drivers may use unleaded regular gasoline with an octane rating of at least 87 AKI. It notes that drivers may notice a slight decrease in performance when using regular gasoline. But, with gas prices on the rise, it’s ok if drivers of the Nissan Maxima choose the less expensive regular gas."

And this is similar, https://www.glendalenissan.com/blog/...-premium-fuel/

 

Thanks for the links, maybe I didn't read her manual close enough I guess now when I fill her car up I won't worry about buying hi test and my wallet does likes regular better