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2005 STS V8 AWD
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7 Posts
Discussion Starter #1
Hi-

I drive a 2005 STS with 91,700 miles. I have used premium fuel with it the entire lifetime of the car. I have heard, not in a direct question, that premium fuel is not required. Is this true? I drive the car gently on a low-traffic commute, and I don't put much effort on the engine. I use 91 octane, and was wondering if 87 was viable.


Thanks!
 

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2005 STS Northstar RWD
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515 Posts
Directly from the owners manual of a 2005. So use of mid grade or regular is acceptable, but will lack some performance.

 

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2006 STS 1SG & 2007 STS 1SE
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13 Posts
Use 'Top Tier' gas. If you notice ping or knock try 89 or a different brand. Premium may be overkill; some do not notice a difference.
 

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2006 STS V8 1SF RWD
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6,490 Posts
I notice no difference between 87 or 91
 

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2006 STS V8 1SF RWD
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6,490 Posts
1BadCadSTS said:
I notice a difference under heavy acceleration between 89 and 93. Never put 87 in mine and never will.
I use 89 95% of the time as it is usually the same price as 87...She gets 91 when she gets her Techron.

Was just stating as I have used 87 and noticed no difference.
 

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'10 CTS4 3.6L Wagon prem; '06 STS 3.6L base; '98 Seville STS
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2,397 Posts
i use premium but i still hear a loud knocking every time??
 

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2006 STS V8 1SF RWD
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6,490 Posts
Mullah88 said:
i use premium but i still hear a loud knocking every time??
Those 3.6's like to make their presence known...Make sure the oil is always full.
 

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'10 CTS4 3.6L Wagon prem; '06 STS 3.6L base; '98 Seville STS
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2,397 Posts
....every time i drive the car, let the engine run...its more of a air puffing (or air being sucked in) sound coming from the right side of the hood, ill make a youtube video of it tomorrow if i get the time
 

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2007 N* STS-4
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530 Posts
I was using 89 for a while when the price of gas was mid $4.00 range. When it came down i went back to 93 and it was noticeably smoother and quicker.
 

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08 STS-4 N* 1SG, 08 DTS Luxury II, 04 Bonneville GXP N*
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3,215 Posts
Where I live, 91 octane is about $0.10/L more than 87. I fill up about every 10 days with a fill averaging about 55L. So, based on this, I figure the annual difference between using 87 and 91 is about $200.00. Not enough that I care. I do believe, although not necessary, I get better performance.
 
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