Premium Gasoline

[skyactiv]

There is a reason why the auto makers want availability of 87 octane to be a thing of the past. They have lobbied to make a new high octane standard. If you want the gas engine to be available years from now. It needs to happen. Otherwise, Joe Dumb that has no problem spending $85K on a 2030 F150 will cry about premium gas, ruin/melt the ring lands in his new truck if he runs 87 octane and blame Ford. People will say, it’s the owners fault. Until his son borrows his dads trucks and ruins a $20K engine when he filled the tank with 87.

 

[kschachn]

There is a reason why the auto makers want availability of 87 octane to be a thing of the past. They have lobbied to make a new high octane standard. If you want the gas engine to be available years from now. It needs to happen. Otherwise, Joe Dumb that has no problem spending $85K on a 2030 F150 will cry about premium gas, ruin/melt the ring lands in his new truck if he runs 87 octane and blame Ford. People will say, it’s the owners fault. Until his son borrows his dads trucks and ruins a $20K engine when he filled the tank with 87.

And the reason for that is trying to meet the ever increasing fuel economy standards. Raising the compression ratio is a legitimate way to increase efficiency. Considering some of the other very expensive and goofy efficiency schemes being implemented it's a reasonable proposal.

 

[jeepman3071]

Not sure what Japanese luxury cars you are referring to, all the ones I service for family/friends require premium (91+ octane) fuel, including some Lexus products.

 

[measureman]

The nice thing about my 2002 Blazer is it runs the same on top tier gas or gas from Billy Bob's cut rate gas station.

 

[vavavroom]

Why are a lot of European luxury cars need premium 91 gas compared to a lot of Japanese luxury cars used regular 87 gas, American luxury cars some require premium. I am leaning more to replace my wife's XC90 with a RX 350

In many European countries, regular gas (91 ROZ) was phased out years ago because of less demand and because producing fewer varieties of fuel was more economical.

 

[Kestas]

I too believe a lot of manufacturers are recommending 91 octane in order to meet CAFE standards. My personal concern is to get from A to B as cheaply as possible. I use 87 octane and let the knock sensor do it's job. The savings with cheaper gas more than offsets any loss in gas mileage. I've been doing this for 10 years with four cars, ever since the price divergence between the two grades of gasoline became wider.

 

[wings&wheels]

Drive the Rx before you commit. We had one for the In-laws and, while it was the perfect car for non enthusiasts, it was absolutely painless to own, it is to date the absolutely least engaging and numbest car Wife and I have ever driven....but we have specific tastes in vehicles. Coming from the Volvo, it will be a much different experience.

 

[loneryder]

I have a Mercedes ML 350 that requires minimum of 91 octane. Since the prices have gone up, I started filling up with 87 every other fill up. Mostly use Costco gas so starting with tank full of 93 and at half a tank fill with 87. Should average around 91. Am I really saving a lot? No but I guess it makes me feel better.

 

[BHopkins]

If the aim is to save money vs. get maximum power, consider whether the extra MPG offsets the extra cost. The spread between fuel grades is getting pretty wide these days.

This depends upon where you live. Here in the Utah/Idaho/Wyoming area, where I travel a lot, most stations have about a $.30 - $.40 spread between regular and premium. But when I visit my son in Kentucky, there is a $.90 - $1.00 spread.

Being a tight wad, I have usually avoided using premium/midgrade fuels. When I bought my wife's Outback, I tried running it on regular. But I noted that the fuel economy suffered, and it didn't run as well. So I switched back to the recommended mid-grade. My E350 requires premium. It also doesn't like lower grade gas I can tell the difference.

I have read articles that say it is not wise to run an engine, designed for a higher octane fuel, on lower octane fuel. While the knock sensor will make the correction, so it is unlikely that you will hear knocking, the engine isn't performing as it is designed. The articles claim that, while this is OK for an occasional fuel tank, it is hard on the engine to be in constant "correction", tank after tank.

 

[MRC01]

People say it's high compression ratios, which is partially true. The whole truth is about high BMEP. That requires fuels that can withstand high pressures without self-igniting. Ignoring units, BMEP is torque per displacement.

However, just because an engine has high BMEP doesn't necessarily mean it needs high octane gasoline. All else equal, it will. But all else is not always equal. There are engine designs that can reduce the tendency for pinging/detonation, enabling higher BMEP on lower octane gas. Another reason this is desirable is that most octane enhancers have lower energy density than gasoline, so higher octane gas has slightly lower energy content. If you can squeeze more out of low octane gas it's more efficient.

For one example, the Mazda skyactiv engines have a 13:1 compression ratio and 75 ft.lbs. per liter of displacement, which is high BMEP. Most cars having that high BMEP require 91 octane gas. Yet the Mazda runs on 87 octane gas. Part of the reason is the unique shape of its piston heads & cylinder heads, and using long tube headers to better isolate the exhaust pulses.

 

[TiGeo]

If it has a turbo, it needs premium. Some companies say you can use regular in them, but it's not a good idea

Why isn't it a good idea if the manufacuterer shows shows it as the min. octane rating? Did it in my Sportwagen for the first few mos. before it was tuned without issue. This is such an internet boogieman/urban legend. So you may get a little timing correction...so what. The slight drop in efficiency will never make up for the sometimes $1 difference in 87 to 93.

 

[DwightFrye]

I live in a small mountain community. There are four gas stations here and only two are top tier major brand refineries. All of them charge a considerable amount more than stations do "down the hill". So whenever I am down in one of the local towns I top up the tank, I have found price differences usually around $0.40 per gallon less than up here for the major top tier stations and ARCO, who is a top tier supplier has been as much as $1.00 per gallon less for 91 octane. A fill up can be as much as an extra gallon more for the same price,
However, I burn at least a gallon getting back up the hill. But at least it makes me feel better not paying the price gougers up here.

 

[KrisZ]

In many European countries, regular gas (91 ROZ) was phased out years ago because of less demand and because producing fewer varieties of fuel was more economical.

Yup, these Europeans sure did figure out how to make gas cheaper.

 

[vavavroom]

Yup, these Europeans sure did figure out how to make gas cheaper.

Right?

 

[edyvw]

I suspect the majority of Lexus vehicles are driven in such a way where the owner wouldn't experience a difference between 87 and 93.

Well, not sure would they notice difference between 50 and 93.

 

[Oillover]

The nice thing about my 2002 Blazer is it runs the same on top tier gas or gas from Billy Bob's cut rate gas station.

+1
I had a 2007 Focus that ran like trash regardless of the grade of fuel it got!
Only difference to me, was how much lighter my wallet was.

 

[TiGeo]

Our '08 Lexus RX350 says to run 91 but we always run 87 without issue or any drop in mpgs that I can tell. If I were towing or in the mountains, sure I'd run 93.

 

[Rmay635703]

Direct injection vs. port injection.

Direct was said to be able to eliminate the need for premium even going so far as to state partial compression ignition (16.5:1 compression) was fine for 87 octane on gdi

 

[gregk24]

Our turbo VW does not require premium but that's all I give it. The manual does not use such wording as "regular / 87 octane recommended", but rather "MINIMUM octane 87". I read that as, don't go below 87 or bad things could happen. Either way it's a small boosted 4 cylinder that puts out full boost at 1400 RPM so it gets premium from a top tier station.

I've never ran regular in it so I have nothing to compare too, but VW rates this at 39 MPG highway for the 2021 model, and we EASILY achieve 45+ MPG without even trying. If you try, 55+ MPG is doable. Maybe that is due to the octane I run, or maybe VW severely underrates the MPG on it, or both.

 

[TiGeo]

Direct was said to be able to eliminate the need for premium even going so far as to state partial compression ignition (16.5:1 compression) was fine for 87 octane on gdi

Like my Focus, GDI, has a 12:1 or so (?) and ran just fine on 87 before I tuned it for 93.