Is 89 Gas with ethanol okay for DTS?

[Superjim]

Originally Posted by Andy1

Andy1 in Calgary again.

The 05, 06, 07 & 08 DTS can use regular gas with no problems.
The engine has knock sensors, basically low frequency microphones in the valley of the V8 block. These pick up the usual knock noises you hear with bad gas, but much sooner. They tell the engine controller to retard the engine timing so no knock damage is caused. If this happens, you will have slightly reduced power and mileage. The Lux 1,2,3, 05,06, 07 & 08 will run fine on regular. The performance version can use reg, or mid gas but really should use premium.
Hope this helps
Andy1

Andy1

Don't take this wrong... I am not trying to start an argument, but my owners manual says........

"Use Premium unleaded gasoline with a posted octane of 91 or higher. You may also use regular unleaded rated at 87 or higher but your acceleration may be reduced and you may notice a slight audible knocking noise commonly referred to as spark knock. If you hear heavy knocking your engine needs service"

On mine it drops the mileage a little better than 2 mpg. It actually costs my a little "MORE" to run regular in it instead of premium. Plus it runs a lot better on Premium. And that I like.

Besides... GM spent a lot of money figuring out what octane fuel it needs and they recommend Premium. Since regular cuts down the power and may cause spark knock... I prefer Premium.

Other cars may be different and may run fine on regular, but mine don't. Sometimes I wish it would, considering the high fuel prices.

Jim from Texas

[Andy1]

Superjim, you are correct, the performance engine uses premium as I said in the last line. "You can use reg but the performance engine needs premium." I haven't noticed any mileage improvement with premium over reg. in my 06 DTS lux2. It may be little snappier in acceleration, but a $5.00 a gallon ($4.20 a US gallon) I don't know if its worth it for me, as our traffic is so bogged down.
I do however get the top tier gas to keep the fuel system and injectors clean.
When it is -38c like this week, I get the 89 with ethanol to keep the fuel system from freezing.
Freezing in Calgary, Andy1

[TulsaVic]

'Scuse me for sneaking in here....but if I've done my math right, and assuming 2mpg better mileage (18 mpg vs 20) with premium for the full tank (18 gal), and just using your $5/gal, the difference between regular and premium would have to be greater than 55 cents per gallon in order for it to be cheaper to run regular. Otherwise you're saving money with each tankful. If I've done my math right....

[Superjim]

Tulsa Vic,

I agree with you. I think it is a false economy to use regular.

At least in MY car it is. I tried it... I don't like it.

It doesn't run RIGHT... it has LESS power and gets WORSE mileage.
Also the owners doesn't say PREMIUM RECOMMENDED in the performance model ONLY. It just says PREMIUM RECOMMENDED
That said... YMMV If it works for somebody else... great, it just don't work for ME. Sticker on mine was over $55,000, I will use the good stuff in it.

Jim from Texas

[JackB]

Could someone explain something to me. I have a 2002 DHS with the Northstar and regular fuel is reccomnended. I get great fuel mileage. That means 30MPG + on a trip without hills. Did GM do something since 2002 to increase the HP and lower the mileage or change axle ratios in the DTS? I have 118,000 miles on the car and am torn between a CTS or a DTS as a replacement. The CTS, even though a lighter car than my DHS gets less mileage which is frustrating to say the least.

[Superjim]

Originally Posted by JackB

Could someone explain something to me. I have a 2002 DHS with the Northstar and regular fuel is reccomnended. I get great fuel mileage. That means 30MPG + on a trip without hills. Did GM do something since 2002 to increase the HP and lower the mileage or change axle ratios in the DTS? I have 118,000 miles on the car and am torn between a CTS or a DTS as a replacement. The CTS, even though a lighter car than my DHS gets less mileage which is frustrating to say the least.

JackB,

I have a 2006 DTS Performance Sedan. (Actually my second one) The first one burned in a fire in my garage.

I have put over 60,000 combined miles on them. I have also driven a few DTS Luxury versions when I have had mine in for service.

My normal driving speed (traffic permitting of course) is 80 / 85 on the road. The Luxury versions get around 25 to 26 mpg with me driving. My Performance Sedan gets around 22.

The Lux versions have a 3.23 final drive ratio and the Performance versions have a 3.73 final drive ratio. The Lux versions therefore turn less rpm at a given speed. Less RPM = better mileage. Usually.

The Performance versions also have more HP, and a Performance algorithm for the transmission for better performance. But more HP combined with the lower final drive ratio means less MPG.

I have also driven a few CTS's in the last 2.5 years. With me driving, they get very little better mileage than the DTS LUX version.

I am getting older and have semi bad hips and lower back. After driving the CTS a couple of hours, nonstop, my hips and back hurts. I have to stop, get out and walk around a bit. I can drive the DTS for five or five hours.. (complete tank of gas) and I don't hurt. The DTS just FITS me a lot better.

As far as your question about Regular vs Premium... some people burn regular with no problems. My car, with my driving style, runs better and gets better mileage on Premium so the cost for fuel is about the same.

If I am not mistaken, around 2003, Cadillac changed the compression of the engine and changed the valve timing for lower emissions while still retaining the same HP.

My owners manual says Premium "RECOMMENDED" but that you can use regular but may experience a slight loss of performance.

Since there is a TON of difference in the CTS and DTS, both in the driving feel and the ride comfort, I would suggest driving one for at least 2 or 3 hours on a little trip out of town to see which one fits you the best. There is not enough difference in the gas mileage to matter. Especially if you are looking at the LUXURY version of the DTS.

Jim from Texas

[joee5]

The last 2 tankfuls I've put in the best stuff I could find,(93), and according to me calculations I've gotten .7 mpg more using the GOOD stuff versus using the CHEAP stuff. Price difference using cash was 2.95 versus 2.71. God Bless, Joe

[Superjim]

Originally Posted by joee5

The last 2 tankfuls I've put in the best stuff I could find,(93), and according to me calculations I've gotten .7 mpg more using the GOOD stuff versus using the CHEAP stuff. Price difference using cash was 2.95 versus 2.71. God Bless, Joe

JoeeS,

In your case... the .7 would translate to 14 extra miles for each 20 gallons. Figuring 14 MPG in the Escalade... that is one less gallon you would buy using Premium vs Regular.

20 gallons Premium @ 2.95 = $ 59.00
20 gallons Regular @ 2.71 = $ 54.20

So... 59.00 - 54.20 =4.80 minus the one gallon you didn't have to buy because of the extra .7 mpg increase = a grand total savings of $1.85 by using regular instead of premium.

My math may be off... but I think it is right. Pick it apart if you can. I would love to be able to save money.

On my car it is right at 2 mpg difference so it is actually cheaper for me to run premium.

JIm from Texas

[FastEddie50]

The manual say 91, so 91 is what I try to use. Occasionally, I'll do a tank of 89.

My 06 DTS has some pinging on acceleration, but it's a lease and, frankly, I don't care.

[Big Jimm]

FWIW - I have ALWAYS used regular gas in everything (except my Harley
Davidsons and various past airplanes.)

This includes my 06 C6 vette and my 08 E-350 Sport. At my age, I'm not
interested in the absolute max hp.

I also change oil about every 12,000 miles. I realize that there are those
who insist on premium gas - and - change oil every 3,000 miles because
“they just feel better doing it.”

But, I feel better not spending the needless extra money! And ... NO
I have NEVER had an engine problem.

Big Jimm