The manual for my 2003 3.2TL says that the gas I put in the car should be at least 91 octane. Wondering if this is really necessary, I am certainly not going to put in less if that is what should be done to just maybe save $4-$5 a tank but was curious. Thanks!

 

Oh boy, here we go again.

This topic has been covered numerous times..., suggestion, use the search function and look for octane threads; that should make the answer to your question as clears as, well, mud (same as if the collective here commented in your thread).

 

This is a high compression engine. The higher octane is necessary for correct and more controllable ignition timing. The engine has a knock sensor so the ECU can compensate to a point if you decide to run less, but only if you have a clean engine and good plugs.

From my research here the consequences of running less than 91 is eventually a clogged EGR system which will cost $300+ at the dealer to clean out. Your plugs will die faster as well if your engine is detonating.

 

I really appreciate the input as a new owner and new to the forum. I did find a thread, as suggested by Horseshoez, and in the end think Chojun makes a persuasive statement. Some of the explanations I found were WAY over my head but that's okay.

While admittedly not educated in the area of fuel, I doubt that there has been some miraculous improvement to 87 octane gas since 2003 to make using it in lieu of the recommended 91 octane advisable or acceptable. Also, while 91 octane here in Nashville hovers around $3/gal, the difference between it and the next level down (89) is maybe 20 cents. While no math wizard, on 1000 gallons of gas that comes out to $200 more I will pay, but mileage might be better, performance should be better and I am guessing any repair I might need as a result of using a lower octane would likely be (as Chojun notes) much more than my lower octane savings.

In the end, I don't want the "penny wise and pound foolish" label to bite me! My TL already has 235K, has paid its dues so I won't force it to drink lite beer. Thanks again for the input! Joining this forum was one of the smarter things I have done this year.

 

A few comments:

• Here in North America fuel is not sold by octane rating; it is sold by AKI rating.
• While fuel quality has improved over the years, 87 AKI is still 87 AKI; and nothing will ever change that.
• If something was done to improve the Anti-Knock Index (AKI) of say an 87 rated fuel, then it would be rated above 87 AKI (as in 88, 89, 91, 95, or even 100).

 

Got it and thanks again. Even though there is 89 available here my impression is it is still best practice to use 91 octane (or I guess AKI)

 

FWIW, my experience and a bit of simple math:
I have a '99 TL. Purchased used in 2003 with 45,000 miles. Car turned 235,000 miles yesterday. Since I've owned it, it has only been fed mid-grade gas (89 octane). I live in the Chicago suburbs and do a 60/40 mix of city/highway driving. I get 21 mpg and my mileage and performance has not changed in my 15 years of ownership.

EGR ports were cleaned back at 70,000 miles under the warranty extension. Pulled intake at 200K when doing valve cover gaskets and EGR ports were clean. Spark plugs changed at 105K and 210K and looked brand new each time. Check engine light has come on twice in nearly 200,000 miles. Once a bad coil pack. 2nd time related to the charcoal canister. As far as I'm concerned, 89 octane gas has not hindered mileage, performance, or reliability.

Now for the math...Today's gas prices at my Shell:
$3.20 for mid grade (89)
$3.75 for premium (93)

10,000 miles driven each year @ 21mpg = 476 gallons
The $.55 price differential between 89 and 93 over 1 year = $262

Personally, I wouldn't think twice about running 89.

 

Oh dear here comes the endless debates. I mean the car does run alright with regular gas which is fine if you don't push it on a regular basis and keep the rpm's low when driving. If you like to drive spiritedly and like to have fun with your car then you'll get the most out of it running premium but it's not a huge difference as the computer compensates timing anyway. All you really need to make sure is that you run top-tier rated fuel which has the best additives to minimize carbon build up.

My TL has only seen premium since new and I really baby the hell out of it so I always put the best I can afford and the car has been burning clean since new, almost no carbon build up on the pistons and valves and when I replaced the cat the outlet side was clean so as long as you put good name brand gasoline you'll be fine.

 

I find mid-grade 89 octane to be a complete waste of money unless its the minimum requirement. The price is always closer towards 91 premium instead of being split down the middle of 87 and 91 and I've never noticed 89 fuel performing any different than 87 regular.

 

Thanks! I really do appreciate all of the input. The reason I was paranoid about the 91 octane is because that is indeed what the owner's manual for my 2003 3.2 TL calls for.

 

A $0.55 difference? Damn. We have a pretty straight 15 cent markup from regular to midgrade to premium here in Utah, which is the primary reason I don't really fret over using premium despite all the hearsay and arguments. At 30 cents more a gallon I'm only looking at about $200 or less per year. Not really too significant considering that just about any port fuel injected engine with a 11.2:1 compression ratio is going to knock with regular. Heck, I still get occasional knock with 93 and that's in an engine with zero carbon deposits.

 

Local prices today around me. 87 $2.85.......89 $3.35.....91 $3.65

I wish I saw just a $0.15 difference between grades.

FWIW this is MD

 

Some localities seem to like to tax the higher AKI grades of fuel disproportionately, here in New Hamster I'm seeing $2.759 for 87 AKI, $2.909 for 89 AKI, and $3.059 for 93 AKI.

 

Just paid $3.89/gal for 91 this morning in WA state . I think 87 was around $3.29.

 

I recently bought a costco membership and for me the price for premium is the price for regular at every other gas station. So i'm basically paying regular price for premium gas.

 

I mooch off my parent's Costco Card every chance I get XD

 

Same here. Costo = $2.82 Reg, & $3.03 Prem. Local Exon = $2.99 Reg. $3.29 Mid. & $3.69 Prem.

 

So jealous of your American prices, here in Ontario I'm lucky to find a gas station charging less than $1.50 a litre for premium (roughly $6.75 a gallon) because our government taxes the hell out of our gas especially since they added a "Carbon Tax" and our dollar is worthless again.

 

It won't last too long. Obama did the same exact thing (not via Carbon tax) but it was not sustainable. The economy can't handle high gas prices. The price of gas factors into E.V.E.R.Y.T.H.I.N.G.

 

There's also some bs going on with Alberta and B.C. Alberta wants to build an oil pipeline through B.C but the B.C premier isn't allowing so Alberta is threatening to cease all oil shipments to B.C and that's causing $1.60 a litre for regular gas in Vancouver >.>