Better Gas Mileage With Premium

[markatty]

I attended the Lexus reception in NJ and part of it included a presentation on maximizing gas mileage. Most of the stuff was fairly mundane stuff, but the woman did say that you can get 4 mpg more using premium gasoline. She said that the RX-400 has to get used to premium and it takes 3 tankfuls before the computer system takes advantage of the higher octane.

So if regular costs $2.20 and you drive 12,000 miles per year, you need 461.5 gallons at 26 mpg for a total cost of $1,015. If Lexus is right and you get 4 mpg more then at $2.40/gal the cost would be $960 for a savings of $55/year. You should also get better acceleration. At $2.54 for premium the cost of gas would be the same.

I tried premium and didn't notice any difference on one tank, other than slightly increased acceleration, so I've used regular. According to this USA Today article regular works just fine.

Anyone actually see any noticable difference?

[RolandB]

I attended the Lexus reception in NJ and part of it included a presentation on maximizing gas mileage. Most of the stuff was fairly mundane stuff, but the woman did say that you can get 4 mpg more using premium gasoline. She said that the RX-400 has to get used to premium and it takes 3 tankfuls before the computer system takes advantage of the higher octane.

So if regular costs $2.20 and you drive 12,000 miles per year, you need 461.5 gallons at 26 mpg for a total cost of $1,015. If Lexus is right and you get 4 mpg more then at $2.40/gal the cost would be $960 for a savings of $55/year. You should also get better acceleration. At $2.54 for premium the cost of gas would be the same.

I tried premium and didn't notice any difference on one tank, other than slightly increased acceleration, so I've used regular. According to this USA Today article regular works just fine.

Anyone actually see any noticable difference?

A salesrep at my dealership gave me the same information a couple of weeks ago and so I let the tank get down to where the low fuel indicator came on, then drove another 12 or so miles and filled up (14.9 gallons and thus about 2 gallons of regular still remained). I will try tank # 2 this week after I get low. I have complete mileage records from day one and am anxious to see what happens. My mileage to date for 21,000 miles is 22.45 MPG so my calculations for +4 MPG is going to be different. The fuel cost delta in Dallas is about 0.20 per gallon. Is there really logic in the car to decide that 'you're a serious premium gas user'?? We shall see! <_<

[Gryphon]

I think the issue is more accurately, lower gas mileage with regular. But there is more to consider than simply fuel mileage. Running regular in a car designed for premium is possible because the engine computer adjusts, among other things, timing, to avoid detonation. I learned my lesson in a previous LS400 that running regular over time causes the engine to run hotter and degrades various engine components. I believe that this was the cause of numerous repairs over the years.

Tom

[Overthehill]

I bought a RX400 three weeks ago. The dealer told me to burn premium, so I have. I'm getting over 28 mpg in mostly suburban driving.

[SOMEONE ELSE'S GOT MY NAME]

I think the issue is more accurately, lower gas mileage with regular. But there is more to consider than simply fuel mileage. Running regular in a car designed for premium is possible because the engine computer adjusts, among other things, timing, to avoid detonation. I learned my lesson in a previous LS400 that running regular over time causes the engine to run hotter and degrades various engine components. I believe that this was the cause of numerous repairs over the years.

Tom

Hugh? Is that for real? So how's the computer know what kind of gas you use?

[retired00]

I think the issue is more accurately, lower gas mileage with regular. But there is more to consider than simply fuel mileage. Running regular in a car designed for premium is possible because the engine computer adjusts, among other things, timing, to avoid detonation. I learned my lesson in a previous LS400 that running regular over time causes the engine to run hotter and degrades various engine components. I believe that this was the cause of numerous repairs over the years.

Tom

Hugh? Is that for real? So how's the computer know what kind of gas you use?

From what I have read, all the car really knows is whether it pings on the gas you use, and it knows the air mass measurements to help adjust fuel flow. Over time, higher combustion chamber temperatures could cause damage or more wear, perhaps, but I think detonation if the car is pinging actually produces the highest temps over time and damages the pistons. If it's not pinging, probably no damage or benefit to the engine, per se, but I do see better performance and mileage on premium. It's what's recommended in the manual, too, although they do permit regular. The switch to that allowance for regular is what generally produced the lower hp ratings on most Toyotas last year, when they tested with full equipment loads and regular gas for the new SAE standards. The 3.5 in the Avalon dropped from 280 hp to 268 hp. Many answers and opinions, mine too, on this issue but premium for me is like replacing tires early and getting frequent oil changes with synthetic. Nice to do, makes me feel better, hopefully has a positive result.

[LexRexBlue]

I was at the same event but had been using regular. Did you get better mileage now that the weather is colder? I decided today to try the premium since the price of gas is lower, but I wonder if it is worth it. They have said that there is no harm using regular. 20 cents more a gallon is going to have to come up with a lot of mpg!

[kmke]

I was at the same event but had been using regular. Did you get better mileage now that the weather is colder? I decided today to try the premium since the price of gas is lower, but I wonder if it is worth it. They have said that there is no harm using regular. 20 cents more a gallon is going to have to come up with a lot of mpg!

We are getting less mileage with cooler temps (40s - 60s) - the engine runs more to keep at operating temp - premium has consistently added 1.8 to 2.6 miles per gallon - we have 24,000 miles on our RX400 and have averaged a true 24.3 mpg - we use middle grade as a compromise for fuel unless heading up into the mountains.

[LexRexBlue]

Well, I filled the tank with premium and low and behold the mpg is down! It has been colder (30s) in the morning to the 50s so I'll give it a try while the price of gas is low. I had been getting 24-25 mpg with regular on mixed driving (suburban and short highwaay stints at 70). (There is about 10,000 miles on the car.) The other factor is when they change the gasoline for the winter the mileage automatically goes down. Stay tuned.

[RX400h]

I've heard other RX400h owners say that 1-2 MPG increases are common when switching to premium. Unfortunately, if you drive over 10,000 miles per year, using premium will either gain you nothing or cost you money, depending on the cost spread between regular and premium.

We use regular consistently and never get less than 24 MPG.

[jerryray]

I am on my 3rd tank or premium.

I have not noticed any increase.

My driving is to and from Manhattan NY 15 miles each way avg 22mpg,

Somtimes I get 24.5 somtimes as low as 21.

Pretty much stop and go all the time.

[RX400h]

I am on my 3rd tank or premium.

I have not noticed any increase.

My driving is to and from Manhattan NY 15 miles each way avg 22mpg,

Somtimes I get 24.5 somtimes as low as 21.

Pretty much stop and go all the time.

Even though I was born in Queens (Astoria general hospital), I knew little about the area, after having been brought up in Connecticut. One day, back a few years ago, my brother Jerry gave me a tour of Manhatten. He attended and graduated from Columbia University and knew the area well.

All I can say is: You are a brave soul - traversing the streets of New York every day!

Dave

[SOMEONE ELSE'S GOT MY NAME]

We are getting less mileage with cooler temps (40s - 60s) - the engine runs more to keep at operating temp - premium has consistently added 1.8 to 2.6 miles per gallon - we have 24,000 miles on our RX400 and have averaged a true 24.3 mpg - we use middle grade as a compromise for fuel unless heading up into the mountains.

My wife drags our overall (15,500miles) mpg down to 26.0 using regular. Ours is AWD. Part of this is from Montana winter driving too. Mostly though it's So. Cal driving. When I was the primary / solo driver I could regularly get 30mpg ... using pulse driving I learned with the prius. My wife though, opts for the cheep gas. I'll see if I can get her to consistently use primium and see if that makes a difference.

[RolandB]

I attended the Lexus reception in NJ and part of it included a presentation on maximizing gas mileage. Most of the stuff was fairly mundane stuff, but the woman did say that you can get 4 mpg more using premium gasoline. She said that the RX-400 has to get used to premium and it takes 3 tankfuls before the computer system takes advantage of the higher octane.

So if regular costs $2.20 and you drive 12,000 miles per year, you need 461.5 gallons at 26 mpg for a total cost of $1,015. If Lexus is right and you get 4 mpg more then at $2.40/gal the cost would be $960 for a savings of $55/year. You should also get better acceleration. At $2.54 for premium the cost of gas would be the same.

I tried premium and didn't notice any difference on one tank, other than slightly increased acceleration, so I've used regular. According to this USA Today article regular works just fine.

Anyone actually see any noticable difference?

A salesrep at my dealership gave me the same information a couple of weeks ago and so I let the tank get down to where the low fuel indicator came on, then drove another 12 or so miles and filled up (14.9 gallons and thus about 2 gallons of regular still remained). I will try tank # 2 this week after I get low. I have complete mileage records from day one and am anxious to see what happens. My mileage to date for 21,000 miles is 22.45 MPG so my calculations for +4 MPG is going to be different. The fuel cost delta in Dallas is about 0.20 per gallon. Is there really logic in the car to decide that 'you're a serious premium gas user'?? We shall see! <_<

I just realized that I never gave the final report on multiple tanks of Premium fuel! I used 93 octane from October through February and about 3,455 miles. I got 22.680 mpg! I switched back to 87 octane and for the next 1,478 miles I got 23.163 mpg! Aghhhhh, I can't explain it!

[RX400h]

I would think that the warmer the climate, the greater the increase in fuel mileage from higher vs lower octane. If you are driving in cool/cold weather, higher octane wouldn't provide any advantage over, say mid-grade or even regular grades under normal driving conditions.

Saying that using super will always benefit you to that extent (+4MPG) is misleading. We average over 24 MPG using regular (Winter months) and mid-grade (Summer months). Perhaps during last week's heat spell when some areas of town saw 108 degrees, premium fuel would've been a good idea, but nnow that it is 75 degrees again, buying premium is not prudent, IMO.

[Jim Nazium]

For what its worth, so far, I have gotten my best gas mileage using Regular. So guess what, I now use regular grade only. If there is a sale (Thursday in my area) where mid or super is on sale, then I might fuel up with higher octane (during hot summer months). Otherwise, regular is fine for me.

Cheers,

MadloR

[bikeandsail]

For what its worth, so far, I have gotten my best gas mileage using Regular. So guess what, I now use regular grade only. If there is a sale (Thursday in my area) where mid or super is on sale, then I might fuel up with higher octane (during hot summer months). Otherwise, regular is fine for me.

Cheers,

MadloR

Ditto, I have done several multi tank tests and Premiun is either the same or less mileage than regular!!

Ron

[RX400h]

Here's something you might want to read:

http://us.lexusownersclub.com/forums/index...c=38975&hl=

Dave

[bikeandsail]

Here's something you might want to read:

http://us.lexusownersclub.com/forums/index...c=38975&hl=

Dave

My Rx400h has 60,000 miles on it. I always use the lowest grade gas of the usually 3 grades and it works and will continue to work fine. The pump labeling is 87.

Ron

[RX400h]

Believe it or not, there are Corvette owners who use mid-grade or regular fuel! However, should there be consequential damage and the dealership takes the initiative to analyze the octane in the fuel you use, the result may be a denial of warranty coverage. I admit that I have used regular gas during the cooler months, but I play it safe during Summer and use mid-grade. In the event that I do need to travel to areas that experience ambient temps over 100F, I will use premium.

[silvercorvette]

I am in the middle of moving to a new state, in LI NY I would do my fill ups on days that the station offered 6 cents off on hi-test so the diffrence in price wasn't very big. In the new state I just moved to gas is 50 to 60 cents less than it was in NY so I really don't care how much extra hi-test costs. I have one more trip to make to NY to pack the rest of my stuff and to put my house up for sale then I will be totally out of here except for visits. All the cars I have owned require the good stuff and I have never considered using the cheap stuff in any of my Vettes or Jeeps.

[Arvada1]

Fellas,

You have a $50,000 car.

If you drive 12,ooo miles/year and get the same mileage with either octane, it will cost you an extra $100 for the year.

Cut out two beers a week and you have made the difference.

[RX400h]

There are three choices of fuel grades. Mid-grade and premium are recommended in the manual. You will achieve lightly better performance when using premium, but honestly, few of us will be able to tell unless we are running our cars at the dragstrip.

Also, these are hybrid cars. If we didn't care about saving money (in the long run), we'd have bought X5s or RX350s!

[bikeandsail]

There are three choices of fuel grades. Mid-grade and premium are recommended in the manual. You will achieve lightly better performance when using premium, but honestly, few of us will be able to tell unless we are running our cars at the dragstrip.

Also, these are hybrid cars. If we didn't care about saving money (in the long run), we'd have bought X5s or RX350s!

RX,

Your analysis of Lexus’s fuel octane recommendations in the O&M manual are not correct. Lexus says regular - 87 pump octane is acceptable and 91 pump octane is recommended. In the US pump octane is an average of ROM and MON. IE 87 pump octane = (91 ROM + 83 MON ) /2.

The proof is using the fuel. There is no knocking or reduced power as a result of using 87 octane.

Ron

[Jim Nazium]

OK, for what it's worth... I have tried several tankfulls of 92 premium unleaded fuel, even tried a couple of 94 Super Unleaded Premium fuel... but, I get the BEST gas mileage using 87 Regular Unleaded Fuel.

I consistantly get 1.00 - 1.5 mpg better with Regular Unleaded, all things being equal. Most of my driving is 50% city and highway (during rush hour).

I average about 31 + or - 1mpg in the late spring, or early fall, and average about 33mpg + or - 1mpg in the hot summer months.

Everytime I ran with super unleaded, I could not attain the same mileage.

My Best ever recorded mileage with Regular Unleaded was 34+ mpg.

My Tire Pressure is about 37-38 psi with Good Year Eagle ResponsEdge.

I see no point in running Higher grades of fuel or spending more on the Octane, given the fact that it is NOT performance in terms of raw speed we are after but rather fuel economy. The HIGHer octane is designed for one thing, and that is to reduce detonation (usually occurs under heavy load). That being said, I do not see how higher octane can yield better fuel economy since we are not Loading up the engine.

Cheers,

MadloR