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The last fill-up I put in regular gas - my mistake. I got distracted with people coming over asking questions about the car. I noticed no difference in performance. I was relieved that everything ran OK. After 303 miles I tanked up with 10.7 gallons of high test today - 28.3 mpg.

Around here the price of regular is ≈$3.79 a gallon. The first station I tried wanted $4.11 for high test. The next one, a BP wanted $4.44 for high test - a 65¢ per gallon gouge. Finally a Speedway charged $3.99. I prefer a 10¢ per gallon step for each higher grade of fuel.
 

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Still cheaper than up here. Regular is at $1.50/litre ($5.69/US gallon), Premium at $1.65/litre ($6.25/US gallon). These are all in CDN dollars. The exchange rate might make a little difference. I'd hate to gas up in Europe though!
 

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You may get away with it as long as you don't push the car.
With a car tuned for premium, there is usually a mileage difference.
Should be cheaper to run premium.
 

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A stock engine should sense the detonation resulting from lower octane gas and retard timing a bit to compensate for the lower octane, right? Still not advisable though.
 

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A stock engine should sense the detonation resulting from lower octane gas and retard timing a bit to compensate for the lower octane, right? Still not advisable though.
Correct. That the 'variable timing' (VVT-i) part of the "All alloy, 3.5 litre DOHC V6 VVT-i, 24 valve engine'. It will be just fine, with reduced efficiency (burn more fuel and give you less HP). Burn half off, then add Premium, and burn it all off. No harm and no foul.
 

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Correct. That the 'variable timing' (VVT-i) part of the "All alloy, 3.5 litre DOHC V6 VVT-i, 24 valve engine'. It will be just fine, with reduced efficiency (burn more fuel and give you less HP). Burn half off, then add Premium, and burn it all off. No harm and no foul.
Was my understanding the VVT-variable valve timing- refers to the adjustment of intake/exhaust valve opening/closing with respect to crank rotation, thus changing torque/power production over the rev range. The retarding of timing from low octane fuel I thought referred to Ignition timing, the timing of the spark plug detonation in reference to piston positioning btdc/atdc. With a low octane fuel, ignition timing would be retarded (closer to atdc) to diminish detonation and its subsequent damage.......? just a thought
 

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Hmm, you are right. Ok, I'm wrong on the letters then (great read on Wikipedia btw), but the engine does have computer controlled variable ignition timing so my point stands. He should be just fine.

Unlike my old '93 Miata where I had to manually adjust timing if I wanted to change octane.
 

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Please don't misunderstand; I was only questioning my own understanding in hopes of clarification.
Also, note your Miata experience and miss(some) of the "good ole days". Would love to be using my timing light, feeler guage, dwell meter etc. that languish in the tool box, victims of the electronic/computer age..........!:)
 

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Please don't misunderstand; I was only questioning my own understanding in hopes of clarification.
Also, note your Miata experience and miss(some) of the "good ole days". Would love to be using my timing light, feeler guage, dwell meter etc. that languish in the tool box, victims of the electronic/computer age..........!:)
You were right, I assumed incorrectly, no foul! lol

Timing light? meter? Just turn the darn thing until it idles smooth. Less science and more gut.
 

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Discussion Starter #11
Please don't misunderstand; I was only questioning my own understanding in hopes of clarification.
Also, note your Miata experience and miss(some) of the "good ole days". Would love to be using my timing light, feeler guage, dwell meter etc. that languish in the tool box, victims of the electronic/computer age..........!:)
I also miss using those tools on our '65 VW beetle - drove it 14 years and sold it for $125 with 175K miles. Due to rust, no floor board under the battery, etc., the dad told his son it should be OK as long as he did not open both doors at the same time.
 
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