Not every fuel system upgrade needs to be built around E85. For WRX and STI owners running gasoline and looking for a straightforward, cost effective pump upgrade over the factory unit, the AEM 340LPH In-Tank Fuel Pump Kit fills that specific role. This post covers what makes it different from the ethanol compatible pumps already covered on this platform, and who it actually makes sense for.
The Real Difference: Gasoline Only, Not Ethanol Compatible
This is the detail that actually separates this pump from the others, more than body size. The AEM 340LPH pumps covered previously, the 65mm version with mounting hooks, are built and tested for ethanol fuels up to E100 and methanol fuels up to M100. This pump is rated for gasoline only. That is not a downside, it is a design tradeoff, since a pump that does not need to handle ethanol’s corrosive properties can use simpler internal construction, which is part of why this pump costs meaningfully less than its ethanol compatible counterparts.
Compact 39mm Body vs the 65mm Variants
Beyond fuel compatibility, this pump uses a compact 39mm outside diameter rather than the 65mm body used on the hook-equipped variants. That smaller diameter fits a wider range of factory sending unit baskets without needing the tight tolerance clearance the 65mm pumps are built around. Like every AEM in-tank pump in this lineup, it is built to a universal specification rather than a vehicle specific fit, so confirming it seats correctly in the actual sending unit basket before installation still matters here the same way it does with the other AEM pumps.
What’s in the Kit and What It Supports
The kit includes the pump, a wiring harness, a pre-filter, internal fuel hose and clamps, an end cap, and a rubber buffer sleeve. AEM rates it to flow 340 lph at 40 psi and states it can support over 1,000 horsepower at 43 psi on a naturally aspirated or forced induction gasoline application. Current draw runs 12 amps at 40 psi and up to 15 amps at 80 psi, the same electrical demand as the ethanol compatible versions, so the wiring guidance covered in the post on the DIY fuel pump wiring kit for WRX and STI applies equally to this pump.
Who This Pump Actually Fits
This pump makes the most sense for a build running gasoline with no plans to switch to E85, where the ethanol compatible construction of the other AEM pumps would be paying for a capability that never gets used. For anyone still deciding between gasoline and E85 for a build, the post on E85 vs pump gas on WRX and STI covers that decision directly, and it is worth settling that question first, since switching to E85 later would mean revisiting the pump choice rather than just adjusting the tune.
For a full comparison against the higher flow external option on this platform, the post on AEM 340LPH 65mm vs 380LPH inline covers how this pump’s ethanol compatible sibling stacks up against the external pump option as well.
Where This Fits in a Fuel System Build
A pump upgrade on its own does not complete a fuel system build. The WRX fuel system upgrades hub and STI fuel system upgrades hub both cover how pump, wiring, rails, and regulator work together depending on the specific build’s fuel type and power goals.
Frequently Asked Questions
Can this pump run E85?
No. This pump is rated for gasoline only. For an ethanol compatible option, the 65mm version of this same 340LPH pump is built specifically to handle E85 and other ethanol blends.
Why does this pump cost less than the ethanol compatible version?
It uses simpler internal construction since it does not need to withstand the corrosive properties of ethanol fuels, which is part of why AEM prices it as a more budget-friendly option.
Does this pump fit directly into a WRX or STI fuel tank?
It is built to a universal spec rather than a vehicle-specific fit, so confirming it seats correctly in the existing sending unit and tank basket before installation is worth doing rather than assuming a direct fit.
Does this pump need the same wiring setup as the other AEM pumps?
Yes. Current draw is the same as the ethanol compatible 340LPH pump, so the same dedicated relay and fuse circuit guidance applies.
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