silvervett

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Does Your Vehicle Use Premium Gas? Buy It or Pay More Later!
Dear Tom, Which octane gasoline is recommended for the '92 Acura Legend LS? (Search 2007 Acura Models) Why would premium gas (approx 100 octane) be required? Do I have to use it? Premium gas is so expensive these days. Jonathan from Holladay, Fla.

Jonathan, That vehicle requires the use of 91-octane fuel. High octane is recommended because the engine is a high performance engine. High-octane fuel is more stable than low octane fuel in the volatile combustion chamber environment of the high output engine. Combustion chamber temps are higher in high output engines because of higher compression ratios. When you use low octane fuel, it has a tendency to pre-ignite or "knock" when it enters the combustion chamber. This causes an explosion in the upper regions of the combustion chamber. Continued use of low octane fuel in a high output engine will result in damage to the engine's cylinder heads and pistons.

Wanna play with the "big boys?" Gotta pay. Put 91 octane in it or suffer the consequences. I didn't take accounting in school, but I do know that the additional cost of high-octane fuel is cheaper than a replacement engine for your Acura in the long run. You can buy an awful lot of high-octane gas for the cost of a new Acura power plant. I looked up the replacement cost of an engine block for your car. Parts: $2,196.74. Labor: 38 hours at say $78.00 per hour (and that's on the low end) is another $2,964.00 in labor plus fluids belts, hoses, and anything else that needs to be replaced. Cough up the extra gas money. Don't be "penny wise and pound foolish." Tom

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Filling Tires With Nitrogen Instead of Air
Dear Tom, I have seen advertisements that promote filling tires with nitrogen instead of air. They claim better mileage and less air loss (air pressure maintained). I own a 2006 Jeep Grand Cherokee (See 2007 Jeep Models) and I am considering having this done. My vehicle also has special valve stems that Jeep calls "tire pressure monitor and warning signal." Will it affect that system? I talked to the Jeep dealer and they were not sure about the advantage of using nitrogen. What do you think? Is it worth it? Jack from Newfane, N.Y.




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Jack, Filling the tires of your Jeep Grand Cherokee (See 2007 Jeep Models) with nitrogen will not have a negative effect on the tire pressure monitoring system. Just yesterday I received a service bulletin from GM stating their position on filling tires with nitrogen. They are of the opinion that it has no ill effect on GM vehicles at all. So if it's good enough for The General, it's good enough for me! I advertise nitrogen filling for a tire company in Buffalo on my America's Car Show radio program. I personally had it done to all of my family's vehicles. Nitrogen is an inert gas that is moisture free. It does not expand and contract (within the range of temperature changes experienced in tires) like air does, so tire pressure does not fluctuate significantly. In addition, it's denser than air, and therefore it doesn't tend to bleed out of the tire's rubber carcass. Tire pressure maintenance should result in better mileage. You ask me, "Is it worth it?" It isn't a necessity; it doesn't make your vehicle any safer; but if you want to maximize tire life and gas mileage, this is one more step you can take. Go for it! Tom

PS he also mentions the check engine light comming on due to gas cap problems. It cost me $75 and a trip to the deaaler to discover that a locking gas cap I put on my Jeep caused the check engine light to come on

The G Man

The RX has a knock sensor in it, using 87 octane will not damage the engine. Nitogen gas is great on airplanes because it doesnt support combusion. If you regularly check your tire pressure, regular air is fine.

mandyfig

Ok, you got me. Next trip to the gas station, I am filling up premium. Now that the gas $ has gone down a bit. Where to get free nitrogen air fill?

cdnewton

G-Man is right on; the knock sensor will retard the timing if you run a lower octane. We run 85 octane (Colorado equivalent of 87) and currently have 84,000 miles on our RX330.

However, to take full advantage of the RX's performance, premium is called for and should be used.

Orzel

iTrader: (1)

On our RX (2005) there is a noticeable difference in performance between 87 and 91 octane, although not a whole lot of difference in fuel mileage. When we travel, given the constant changes in elevation we encounter in the Western states, we always use premium. There appears to be a significant performance difference at altitude between using the regular grades and the "high test" grades. Around home (generally at sea level) I tend to use midgrade and on the open road average about 24MPG, but have seen 26+.

We also runtrogen in lieu of “air” in the tires on both the RX and our IS. No issues with the TMPS on either, and the IS has individual wheel sensors.

Grumpa72

I read the posted articles and I tend to agree with them with one exception; most "high peformance" engines do indeed have some version of a knock sensor that reduces timing allowing us to use regular gas without any ill effects. I am talking only about non-blown cars, those without turbo or superchargers. I am a shade tree mechanic and read as much as I can on this stuff but I am convinced that the arguement the author makes, is overblown. Basically, he is saying pay me know (premium fuel) or pay me later (replacement engines). My '05 330 clearly states in the owner's manual that regular gas is just fine for my car. No caveats, no "buts", or "excepts". It does go on to say that a slight loss of performance can be expected. I can live with that, especially since I didn't buy this car as a performance car. I bought it as a luxury SUV with a great ride, safety features I can live with, and my wife as a primary driver.

I would suggest that if you live in a high altitude environment, regularly pull a small trailer, or feel like driving like you stole the car, then premium fuel is the way to go.

Gary
just my opinion.

JasDmw

Ok, I have an '08. Manual and gas door sticker indicate premium is needed. yet as I understand it, this is basically the same engine as in the Sienna and many other Toyota products, which run regular. Appears the question is; is this engine in the Lexus line a "high performance" engine? Or do they need us to run premium so we can get the performance of the (I think) 277 HP vs the 270 HP in the Sienna ad we've all seen?

So far I've been trying both and have just recently seen amazing mileage with regular (Shell) as opposed to E10 premium. This is confusing!!

As far as Nitrogen goes. the tire guy I use, from a reputable large local chain, suggests Nitrogen is great for F1 use. For us everyday folks, it's apparently another one of those gimmics. Because " the general" doesn't have a problem with it, doesn't mean we need it or that it makes a big difference. Dealerships are using this as the newest "pack" to make another bit of profit from us when we buy. That goes both for car dealerships and less than reputable tire shops. I see Costco is even offering it.

Grumpa72

While your engine may be "basically the same engine" as other Toyota products, the engine performance map may be different. For instance, when I was a teen, Chevy offered the 327 ci engine in the family sedan that was "basically the same engine" offered in the Corvette. What was different was the carb, the cam shaft, the vacuum advance and distributor. Today, you can often have identical components in your Lexus that are in a Toyota but the horsepower is different (and presumably the octance requirement) because the computer is doing all of the things that the old carb, distributor and vacuum advance did. As I understand it, the biggest thing that can change in an engine is the timing and the ignition map which generates more horsepower. When we generate more hp, you can sometimes get detonation which is not a good thing. To preclude that, manufacturers use premium gas. Obviously, if you take your Lexus to Timbuktoo (sp?) and all they have is rot-gut gas, then your engine has to be able to run on it. From what I know, that is why the manufacturers have a knock sensor in their electronic engine package.

My '05 330 clearly states that regular gas is just fine as long as the slight loss of performance is acceptable. Your newer car my not run well on regular but the easiest way to test this is to let your fuel get real low and add a half tank of regular gas and do your normal driving. Believe me, you will know if your car has detonation. Sounds like marbles pinging around in a large can. Some folks also call it a diesel sound.

harleydjce

There have been a couple of threads on this. Power increases aside from Premium gas, I would be more concerned with better quality additives from say Shell V-Power (not all premium gas is "premium" in respect to additives) to keep the engine as clean as is possible (nothing's perfect). As for Nitrogen in the tires, this is my 2nd RX where I have run Nitrogen and I couldn't be happier. A tire dealer should be able to do this for a modest charge (One benefit I have found is that you don't need to check tire pressures much say every six months)

jaydunn

The air I put in my tires is already 78% nitrogen. Selling nitrogen for ordinary street use is just another way for tire/car dealers to make an easy buck.

Lexmex

One significant value from nitrogen use is from flat tires. I have had a few nails go all the way through and only upon inspection (as I do every week) did I notice. Had that been air (like occurs frequently with other vehicles), I am sure I would have been changing a tire, but I love those big molecules and the fact you can get a tire patched for $5 USD here, no worms used.

The G Man

Where can I get me some of that desiger air

JasDmw

OTOH, I had a nail in my tire a few weeks ago. The TPMS picked up the leak of good 'ol O2 and forced me to investigate. I found a nail in the tire, close enough to the edge to get the tire replaced under the road hazard warranty. There is a scenario whereby not noticing a nail is in the tire that could possibly keep one from realizing that there is a problem. Relying on nitrogen to ignore the tires and/or pressure is potentially dangerous.

I'm in the camp that argues it's a dealer pack/profit enhancer with little real world value.

The G Man

I agree, the hassle and the cost out weights the benefit of using nitrogen in cars.

Lexmex

I am not using it to ignore the issue, but rather using it as a safety feature. You really don't want to stop to change a tire in some places in Mexico City, make that most places. First, you can get robbed. Second, the police will cite you for infraction, even if changing a tire as there are a whole bunch of rules about doing this that seem to be arbitrarily enforced. BTW, it is a law here that you must have a spare tire and the equipment to change it.

I certainly wouldn't pay more than about $25 USD for all 4 tires, but what I was noticing up here when I used air was that I was losing about 1 psi per month and that stopped, about 1 psi per every 6 months with nitrogen more or less. Plus, my tires seem to be lasting a whole longer than previously with air.

Run flats sell REALLY WELL down here due to the safety issue.