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I drive a 2005 A4 1.8T automatic. So far, have only used premium. Is regular unleaded gasoline an option? Would I notice any difference in performance (I'm not a leadfoot, by any means)? Is premium gas suggested by Audi / users for any other reasons (engine / component longevity, etc.)?

Any advice would be great. Thanks.

- - Scott
 

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i think audi recomends premium in the 1.8t but its not required. you should check your manual, itll say there. i burn premium in my allroad and jetta .. its required in the 2.7t allroad and recomended in the VR6 jetta... i've ran both premium and regular in the jetta and i feel like i can feel a difference. no more than maybe 3hp tho. if you dont want to put in premium, you can get away with the middle grade.. i wouldnt go with regular unless its from like Mobil or Shell
 

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audi says the 4.2 should burn premium all the time.. i'd say put premium in it all the time unless you get a very good midgrade.... mobil probably.
 

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Free advice from a VW 1.8t owner (Still shopping for my first audi) (which is the same powerplant as your car) - use low test gas with this engine and the only down side is you make less power. Cheap gas causes knocking and the 1.8t ECU is great at reacting by (I think) retarding spark, and it may also allow for less boost. The ECU did this seamlessly in my Jetta and in also my sisters 04 passat.

Can you feel the loss of power when you use cheap gas? Yes. A lot? Well, no not a lot but yes its pretty noticeable.

Can you feel any other negative? No. The ECU and knocksensors work as advertised.

I would estimate more than 3 hp loss; my seat-of-the-pants dynamometer suggests 15 hp difference from 87 octane to 91 with that 150 hp 1.8t.

You have nothing to lose so tank up with 87 and see what happens. You might be OK with how it feels.
 
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