Since I don't know what I want, I'll ask this question broadly, as well as specific.
looking at a few different Lexus. Current one i'm considering is a 2001 GS300. 2jz straight 6. same engine as supra. The Lexus version calls for premium gas. the supra version calls for 87. Looking at Lexus requirements, every Lexus calls for premium gas. I seriously doubt the compression is higher on the Lexus version, so why in the world does it need premium? I tried searching on Lexus forum. That was about as successful as balloon boy. If its in the manual, you're not supposed to question it apparently.
I had an IS300, same deal. I usually put mid-grade in it, unless it was hot weather or I was planning on driving it hard. Got horrible mileage either way.
Sightly different toon, smoother and less downshifting on premium to give that refined Lexus experience would be my estimate. Toyota seems to play pretty ambiguous as to the "why"
My 2015 Land Cruiser calls for regular in the manual, LX570s call for premium. My old Land Cruiser and its twin LX470 both called for premium while the V8 4 Runner with the same engine called for regular. I noticed my old LC ran noticeably poorer with regular.
Driving for 10/10? Use premium. Daily derping for Suzy Q Homemaker? She damn straight isnt putting premium in it, and all the raggedy 15 year old Lexuses (Lexi?) in the hood don't run on premium and they are still pretty thick on the ground here.
Most of them "recommend" 91, but only require 87. However, in cases like that, a lot of times the car will get better MPG on premium (sometimes enough to cancel out the cost difference). Premium gives a couple extra HP too. Basically, it can run on 87, but it'll be frequently pulling timing to do it.
If you do a roller inspection, it may fail for NOx on regular. Nissans in particular were good for this, and it was often an uphill battle to suggest that the emissions failure was because the wrong fuel was used. The usual response was "it all comes out of the same pump so it's a scam."
In reply to Tyler H :
you aren't kidding on the horrible gas mileage. I kinda expected a midsize car to get better than 18mpg.
most modern cars are perfectly happy running on regular old 87.. but their electrons are busy pulling timing to make it so. Give it the good stuff and you can gain power and economy as the engine can run as designed.
I remember back in 2000 I had a Hyundai Tiburon. It called for regular gas, I only ever put 93 in it. I used to consistently beat the EPA estimates by more than a few miles per gallon when most people on the forums for the car were at or slightly under. Yes, they used 87 and would tell me I was an idiot for putting 93 in.
Ha, just this morning the Montero Limited needed gas and it calls for premium. It is one of the few cars I have that call for it. I have run regular 87 in it before, however it has 215k miles and runs perfectly so I generally dislike giving it the cheap stuff since I don't want to give it a reason to not run perfectly and I don't want to somehow, "over labor" the engine. It may not actually work this way but its my thought.
Today it was damn low and I put in 20 gals of premium 93. Sam's Club ftw. Sam's is my "go-to" for premium. They only sell two flavors, 87 and 93. Today, the 87 = $2.05; the 93 = $2.35. A 30 cent delta. Many stations have a 75 cent delta. If I am at a station that is a 75 cent delta then I just buy regular; but only as much as needed.
Here's another thought that really bothers me...
My local county auditors office of weights and measures tests and puts a seal of approval on gas pumps. What they are there to assure is that 1 gallon really equals one gallon. What I wished they also tested was that on stations that blend 87 and 93 to have a mid grade of 91... that it really is 91.
Knurled. said:
If you do a roller inspection, it may fail for NOx on regular. Nissans in particular were good for this, and it was often an uphill battle to suggest that the emissions failure was because the wrong fuel was used. The usual response was "it all comes out of the same pump so it's a scam."
I'm trying to figure out how a car would fail NOx due to regular fuel instead of premium....
Tells me that Nissan is doing something really wrong.
BTW, I'm agree with rskifkin- so at least try regular. You may or many not notice a difference. If you do, then stick with premium. If not, stick with regular. IMHO, Toyota is more robust than Nissan, so I expect that the Lexus will not hurt anything.
John Welsh said:
Here's another thought that really bothers me...
My local county auditors office of weights and measures tests and puts a seal of approval on gas pumps. What they are there to assure is that 1 gallon really equals one gallon. What I wished they also tested was that on stations that blend 87 and 93 to have a mid grade of 91... that it really is 91.
They are supposed to check for octane rating- and the number is a minimum number. So the 87 pump could have 91 in it. When I worked at Chevron, they told me it was a regular advertising thing to do of putting much higher octane fuel in when doing a credit card drive. So regular would have 93 and premium would have 98 in it. Back then, cars were not well tuned, and many high end cars did require premium- so you would notice a change in how it ran.... Funny how that was.
I run 87 in my Pathfinder, the cap reads ( for maximum performance use 91 octane), not required but will make more power. It doesn't need maximum performance.
My 89 M3 and Grand National ran like poo on 87, only did that once in each due to availability.
With my selectable tuner in my Mustang #1 will run on anything #'s 2-4 need premium as the timing comes in quicker or something.
Infiniti says you must run premium in my G37. Not willing to risk it to run 87. I just suck it up and buy 93 (which is what's available here)
alfadriver said:
Knurled. said:
If you do a roller inspection, it may fail for NOx on regular. Nissans in particular were good for this, and it was often an uphill battle to suggest that the emissions failure was because the wrong fuel was used. The usual response was "it all comes out of the same pump so it's a scam."
I'm trying to figure out how a car would fail NOx due to regular fuel instead of premium....
Tells me that Nissan is doing something really wrong.
Cadillac 4.9s were also really bad for this,too. NOx through the roof on the wrong fuel. The Nissans (and Caddys) would specify in the fuel door to use premium fuel only. Might have been on the instrument cluster as well, it's been a while since I have seen a pre-OBD2 DOHC Maxima.
Theorize all you'd like, I just call 'em like I see 'em. Putting 92 or 93 in would clear them right up, when we were allowed to do that. The general diagnostic for high NOx as an emissions failure is to verify ignition timing, fuel control, cooling system integrity, EGR function, and fuel quality. If all those are good, THEN the catalyst is suspect, although I have never seen an OE cat fail in such a way that it has high NOx but good HC and CO. (Aftermarket cats are another story - those would very often fail NOx even when everything was correct)
In reply to Knurled. :
It's not that I don't believe you, it's just that I think its hard to screw it up that bad. Knowing what is done via premium or regular, what are they doing???
In reply to alfadriver :
The Caddys I could easily blame on poor combustion chamber design and high HOT exhaust residuals due to the cruddy ports and restrictive exhausts. Nissan didn't have any excuse other than maybe shaving the reduction part of the catalyst to the bone in order to save money.
These were the same cars that would do all sorts of weird things when cranking, because the original engine ground setup was poor. WEIRD things, like you're watching the crank signal on a scope and it goes haywire when the starter is engaged. Move the ground two inches and it was fixed. I forget my alphabet soup to remember if it was the VG30DE or a VQ engine.
Apropos to the thread, check out what the compression ratio is.
On my 10:1 Golf, running 93 got more savings in fuel economy than the expense in fuel. This was when 87 was $3.90 and 93 was $4.50. Called for 87.
On my 8.5:1 Quantum, it actually got better fuel economy by dumping half a bottle of cetane enhancer in per tank to drive the octane below 87. But at $9 a bottle, it neatly canceled out the economy benefits. And it didn't much like being at more than half throttle unless it could accelerate.
On my 8.5:1 Volvo, I... er... had been running 93 because 15psi boost. Could get 27mpg if I tried hard. I decided to try 87 (hell, there are no "Premium Only" stickers...) and I have seen 30mpg, and my last trip home from Columbus got 29.2 without trying. Car is EPA rated at 23mpg highway.
In reply to Knurled. :
Or how about the BRZ/FR-S/GT86 trio? Stock FA20 engine can "take" our 91 octane but was made for 93- and one of the best mods for it is to swap the fuel pump and fuel map for E85. A friend of mine planning on the swap says says the mileage on E85 should be around 20 for most city driving that he does with a bump in power, and considering the compression of that engine is 14:1 I don't doubt that.
Knurled. said:
Apropos to the thread, check out what the compression ratio is.
The compression ratio on the supra, and the gs300 are the same. 10:1.
on an unrelated note, this article from jalopnik just came out. The desire for a GS300 is increasing. The one I have my eye on is about 500 miles away, but in GRM mileage thats like 10 miles away.
https://jalopnik.com/master-tuners-engine-teardown-explains-why-the-toyota-2-1832540836
GIRTHQUAKE said:
In reply to Knurled. :
Or how about the BRZ/FR-S/GT86 trio? Stock FA20 engine can "take" our 91 octane but was made for 93- and one of the best mods for it is to swap the fuel pump and fuel map for E85. A friend of mine planning on the swap says says the mileage on E85 should be around 20 for most city driving that he does with a bump in power, and considering the compression of that engine is 14:1 I don't doubt that.
FA20 is 12.5:1
If the motor is still naturally aspirated it does not need a fuel pump to run E85. The stock system has plenty of headroom. It has so much headroom in fact, with a supercharger or turbocharger on the car, the stock fuel system is capable of supporting nearly 300whp.
All you need to run E85 in a Twin is the tune.
z31maniac said:
GIRTHQUAKE said:
In reply to Knurled. :
Or how about the BRZ/FR-S/GT86 trio? Stock FA20 engine can "take" our 91 octane but was made for 93- and one of the best mods for it is to swap the fuel pump and fuel map for E85. A friend of mine planning on the swap says says the mileage on E85 should be around 20 for most city driving that he does with a bump in power, and considering the compression of that engine is 14:1 I don't doubt that.
FA20 is 12.5:1
If the motor is still naturally aspirated it does not need a fuel pump to run E85. The stock system has plenty of headroom. It has so much headroom in fact, with a supercharger or turbocharger on the car, the stock fuel system is capable of supporting nearly 300whp.
All you need to run E85 in a Twin is the tune.
Seriously? Do you have links to back that up? 'Cause if my friend only needs that tune instead of a ~$700 kit I think he'll take that instead.
The 3.6 VR6 in the Passat calls for premium fuel and has ingested a steady diet of 87 for the last 3-4 years without a hiccup. That's running a 12:1 compression ratio.
The NC calls for premium despite being a fairly mundain MZ Ford mill and only a 10.8:1 CR. I'll give it some 87 this fill and see how it feels.
The Jag calls for premium with its Ford Contour motor at 10.5 CR and bringing it up from Florida it seemed happy enough on 91 octane.
My feeling is that unless your car is running forced induction it can get by just fine on 87.
GIRTHQUAKE said:
z31maniac said:
GIRTHQUAKE said:
In reply to Knurled. :
Or how about the BRZ/FR-S/GT86 trio? Stock FA20 engine can "take" our 91 octane but was made for 93- and one of the best mods for it is to swap the fuel pump and fuel map for E85. A friend of mine planning on the swap says says the mileage on E85 should be around 20 for most city driving that he does with a bump in power, and considering the compression of that engine is 14:1 I don't doubt that.
FA20 is 12.5:1
If the motor is still naturally aspirated it does not need a fuel pump to run E85. The stock system has plenty of headroom. It has so much headroom in fact, with a supercharger or turbocharger on the car, the stock fuel system is capable of supporting nearly 300whp.
All you need to run E85 in a Twin is the tune.
Seriously? Do you have links to back that up? 'Cause if my friend only needs that tune instead of a ~$700 kit I think he'll take that instead.
OK. I literally Googled "BRZ E85 tune" and found this immediately.
https://www.delicioustuning.com/Stock_BRZ_FRS_86_Breaks_200whp
https://www.delicioustuning.com/catalog/85
EDIT: I'll reserve the snark. Needless to say, your friend needs to do some research and educate himself.
KyAllroad (Jeremy) said:
The 3.6 VR6 in the Passat calls for premium fuel and has ingested a steady diet of 87 for the last 3-4 years without a hiccup. That's running a 12:1 compression ratio.
The NC calls for premium despite being a fairly mundain MZ Ford mill and only a 10.8:1 CR. I'll give it some 87 this fill and see how it feels.
The Jag calls for premium with its Ford Contour motor at 10.5 CR and bringing it up from Florida it seemed happy enough on 91 octane.
My feeling is that unless your car is running forced induction it can get by just fine on 87.
But do A-B-A testing and do the cents per mile math, is what i was getting at. You may find that a fuel economy increase on premium will make the actual cents/mile drop, and spending less on fuel is the goal, is it not?
premium is 25% higher here. I'm pretty confident you aren't seeing a 25% mpg increase with premium.
02Pilot
SuperDork
2/12/19 3:22 p.m.
Now I'm curious - I'm going to have to try switching my 128i over to regular for a tank or two to see what the effect on MPG is. FWIW, mine is an N51 SULEV engine, so it's 10:1 instead of 10.7:1 for the standard N52. At the station I normally use 93 is about 18% higher than 87. If I have the chance I'll throw my scanner on to check timing advance at idle and WOT with both fuels to see if I can pin down any clear retardation with the lower octane.
