The cost of the G100UL STC (Supplemental Type Certificate) varies depending on the aircraft’s engine and horsepower. Generally, it is priced at around $2 per horsepower. For example, for aircraft like the Cessna 210, Cirrus SR22, and Piper PA-32, the STC costs approximately $600
The price of G100UL avgas is estimated to be about $0.70 to $1.15 more per gallon than 100LL avgas. This price difference is expected to decrease as G100UL becomes more widely available. Additionally, the higher fuel cost may be offset by lower maintenance costs due to the absence of lead.