I am just getting into rc cars and I am getting a 1/10th scale 4wd buggy. What percentage of nitro should I use and if I start using 1 percentage, can I switch later?

1 percent nitro.......................

the usual nitro content is
20%
the engine will run on anything from 0% to, well,
as much as you can find i suppose

but that will affect engine performance

low nitro content fuels
will lower performance
high nitro content fuels
will decrease engine life

the manufacturer of whatever you buy
will reccomend a percentage of nitro
and oil
that you should run
so, i'd say to run that

and
yes, you can change nitro content later
either up or down
with no harm to the engine

it will just need to be retuned

ok cool so i have read that the .18 engine usually runs best with the 20% nitro and .21 and up run best with the 30% is that true?

Not really, you'll just get more power with the 30% compared to the 20%. Anything between 10-25% will run just fine.

my brother runs the 30% should i use that or would you suggest the 20%

30% will run in .18ci and .21ci engines just fine. All you need to do is retune the engine and maybe also change the plug and/or add/remove a head shim. I personally use 30% for all my engines, .12ci to as large as .30ci.

ok thanks

Well I use 25% LRP racing fuel for my .18ss after the modifications I've made. Before that I was using 16%.