how bad is it to be running a 93 Octane tune but using 87 gas?

[MercNasty]

Am I harming the car by doing this? should i change the tune to 91 to be safer or should i just change it to 87 since thats what im using. The car is my dd and i drive about 50 miles daily round trip so im not even thinking about putting a higher grade of gas in it right now due to the price of gas. Let me know your thoughts.

[SpartaPerformance]

You run the risk of detonation which can blow your motor. If you're going to run 87 then run the 87 tune.

[RF Overlord]

^^^what he said^^^

The knock sensor can pull timing just so far...if you exceed that limit then you get to pull your engine and put another one in.

[Bluerauder]

Originally Posted by MercNasty

Am I harming the car by doing this? should i change the tune to 91 to be safer or should i just change it to 87 since thats what im using. The car is my dd and i drive about 50 miles daily round trip so im not even thinking about putting a higher grade of gas in it right now due to the price of gas. Let me know your thoughts.

Since you asked .....

You will NEVER drive the car far enough to save enough money to cover the cost of the engine WHEN it fails. I'd suggest that you park the MM and get a daily driver that runs on 87 that can do the duty and not break your bank. The owners manual says "Minimum 91 Octane" .... anything less and you are pushing your luck. The 4.10 gears are probably costing you 1-2 MPG (about $2.00 per day) ... put the 3.55 gears back in and you may be able to afford the 91/93.

Worst case scenario is to sell the MM and get something more in line with your current situation. I suggest doing it before the engine blows. You asked.

[IwantmyMMnow!]

Originally Posted by Bluerauder

Worst case scenario is to sell the MM and get something more in line with your current situation. I suggest doing it before the engine blows. You asked.

If saving $$$ on gas is of great importance to you, I agree with Charlie...park or sell your MM and get a 4-banger to DD with. Running 87 octane on a car that requires 91 minimum AND running a 93 tune sounds like the perfect storm for eventual engine-go-boom.

[MercNasty]

Thanks Sparta and RF for answering my question lol Bluerauder's response was a lil far fetched. I think ill just change the tune to 91 and start putting 91 gas in there. I think i can pay for 91 with a food stamp card.

[Bluerauder]

Originally Posted by MercNasty

lol Bluerauder's response was a lil far fetched.

Do the math if you think my response was far fetched?

[IwantmyMMnow!]

Originally Posted by MercNasty

Thanks Sparta and RF for answering my question lol Bluerauder's response was a lil far fetched. I think ill just change the tune to 91 and start putting 91 gas in there. I think i can pay for 91 with a food stamp card.

You asked for our thoughts/opinions about your situation...you may not like what you hear.

[Hadamustang1]

Originally Posted by Bluerauder

Do the math if you think my response was far fetched?

$2 to $3 bucks a tank.. x how many tanks . new motor cost?

I think he was right on the mark..

[MercNasty]

i didnt any questions regarding any math or what i could afford or if i should park, sell or get another DD. I forgot how extra some of the comments can be on here. Thanks again Sparta and RF for answering my question.

[a_d_a_m]

Originally Posted by MercNasty

I think i can pay for 91 with a food stamp card.

...are you serious?

[MercNasty]

lol no man that was a joke.

[a_d_a_m]

...phew! Good!

As others have said you're best off running what your car is tuned for.
And if you do the math, you'll see that it really isn't much more expensive to be running 93 vs. 87. Here, assuming a 16gal fillup, that'd be $3.20/tank. Better than an engine rebuild.

[03sport007]

Trust me I'm not advocating this at all but if the op was very gentle on the throttle and avoided lugging the motor wouldn't he be ok? I would stay away from heavy acceleration or big hills but I would think driving on flat terrain with grandma starts should be doable.

Again not something I would personally do or suggest she speaking hypathically.

[MercNasty]

Thanks Adam, now thats some math that ill consider. I guess there isnt that big of a difference $62 for a fill up with regular and $67 for super. looks like i start putting 93 in it.