I have watched this discussion and some points are really on the mark but others are out there. First off, fuel, Are there gains to be had? of course there are but it's much less than you think. I took one engine and every fuel additive I could get my hands on including 1.4 dioxin. In any concentration that would pass the Digatron DT41 tester which wasn't much to show a 30 point variance. There was never more than a .05 to .10 hp gain. ( That's tenths of a HP in case your confused.) We then tried 7 different enhanced fuels, there were some interesting results. All but one made the same power as regular unleaded fuel. Some made a little more on top others a little more on bottom, but none made more than a .15hp more than plain ole unleaded fuel. To answer the first question, yes we tried different jets, no we never changed the timing. All these fuels also failed the Digatron tester, including the one that did make a .5hp difference, which by the way nearly blew the tester up it was so far off. So the results basically told us that any fuel or additive that could get passed the Digaton did not make any difference at all and even hurt HP sometimes. Despite those who swear otherwise yes 1.4 Dioxin is detectable in any amount that makes the slightest HP gain. So if you use it you are only trying to kill your competition and the spectators, literally. Hear is the real kicker, we had bigger gains from pure E85 and a mixture of 2/3 gas with 1/3 methanol made a bigger gain of X2 or more, than any additive or fuel besides pure methanol.
So fuel and fuel additives are a waste of time and money if you test properly. I am sure some will disagree but you will have to show me proof.
Now oil is a different animal all together and you don't have to build it real loose to see big gains. This is where huge gains are made mainly because everyone has been convinced that oil can't be tested in a gas engine. It's total BS, oil can be tested. We put fresh Power Plus oil in a engine and made 5 dyno pulls, then added 2 ounces of gas to the oil and made 5 more pulls. Then heated the oil to 300 degrees and it did not burn, it did not even flash. So don't even waste your time trying to convince me you can't burn oil in a clone, I know better. If your oil burns it wasn't legal to start with and you probably have some pretty nasty additives in there. Oil companies and builders are banking on this myth that you can't test oil and are deliberately producing these oils and advertising their "superior performance". Now on the flip side there are additives that will pass the flame test and can produce up to .6 HP on top end without sacrificing protection against wear. Some are even nonhazardous to your health with the exception that they tend to explode sometimes. The point being these are oxygenators which can greatly increase power but are exorbitantly expensive. These compounds are highly controlled and very hard to obtain. Very few racers are willing to pay $120 to $150 per gallon for oil, but some do and you are racing against them.
So while gains are extremely small fuel still needs a lot of attention for health reasons. Oil is where the real power is made and the flame test will catch most of it, but not all. A pump around will stop 90% of your fuel problem, Oil is what is hard to control.