All Tools
E85 & Ethanol Blender
Running E30, E50 or full E85? Work out exactly how much E85 to pour into the tank you have — or how to build a batch from empty — with octane, stoich AFR and cost included.
L
L
% E
% E
Pump & price settings (E85 is rarely exactly 85% — real pumps run E51–E85) ▾
% E
% E
RM/L
RM/L
Add E85
9.09 L
Final mix volume
34.1 L
Final ethanol content
E30
Added fuel cost
RM 26.36
Estimated RON
~99.8
Stoich AFR of blend
12.99
WOT target (λ 0.85)
11.04
WOT rich (λ 0.80)
10.39
Rule of thumb: every 10% more ethanol raises stoich demand ~0.5 AFR — an E30 tune needs ≈ 5–8% more fuel volume than E10 at the same lambda.
Good to know
- Real pumps are not exactly E85: US spec allows E51–E83. Set the actual pump content if you can measure it (an ethanol test tube is RM20 well spent).
- The maths is volumetric and linear — final ethanol % is measured against TOTAL volume after mixing, not the starting litres.
- Blend RON is interpolated linearly; the real world is close but not exact because ethanol’s cooling effect and octane add more than linear at the top end.
- E10/E85 cars handle blends automatically only within their flex-fuel range — beyond that, fuelling and ignition need a proper tune.