Successful Tips for Burning Straight Vegetable Oil in Diesel Engines

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Successful Tips for Burning Straight Vegetable Oil in Diesel Engines

Vegetable oil can be used as diesel fuel just as it is, without being converted to biodiesel. However, it’s around 11 times thicker than diesel, doesn’t burn as easily in the engine, and has very different chemical properties and combustion characteristics — so it can damage engines. Despite that, it can be, and has been, used successfully.

Short answer: straight vegetable oil (SVO) can run a diesel, but because it’s thick and burns poorly it brings real risks — injector coking, carbon, sludge, oil thickening and fuel bug. Older indirect-injection (IDI) diesels suit it best, and FTC Decarbonizer (for clean burning and as a biocide) plus Flushing Oil Concentrate (to control sludge) are key to making it work.

Although some diesel engines can run pure vegetable oils, turbocharged direct-injection engines are prone to more problems. Older IDI diesel engines are generally more suitable for SVO use — the likes of 1980s Mercedes, Toyotas and VWs, to name a few.

SVO vs biodiesel vs HVO — not the same thing

It’s worth being clear, because these three often get confused:

  • SVO (straight vegetable oil) — raw, unprocessed oil. Thick, burns poorly, and the subject of this article.
  • Biodiesel (FAME) — vegetable oil or fat chemically converted (esterified) into a thinner, more usable fuel, often blended with diesel (B20, B100).
  • HVO (hydrotreated vegetable oil / renewable diesel) — oil or fat refined into a paraffinic hydrocarbon that’s a clean, drop-in replacement for diesel.

The good news: CRD Fuel Enhancer is suitable for use across bunkered fuels, heavy fuels and bio-blends — including biodiesel and HVO. Even though HVO and biodiesel are cleaner and far easier on an engine than raw SVO, they aren’t immune to water, microbial “fuel bug” and filter-blocking issues — especially when switching a tank or fleet over from fossil diesel, which can dislodge legacy deposits. CRD Fuel Enhancer and FTC Decarbonizer (a strong biocide) help keep the fuel system clean and protected across all of these fuels.

Problems to Manage for a Successful Outcome

  1. Coking on the injector tips — to the point that fuel atomisation doesn’t occur properly, or is prevented by plugged orifices. This comes from the poorer atomisation and combustion of the thicker SVO, and causes difficult cold starts, poor performance, smoke and short engine life. FTC Decarbonizer in the fuel has been shown to provide major benefits with SVO — it gives faster, easier ignition, actively burns off existing injector-tip deposits, and burns the SVO much cleaner so far fewer deposits form.
  2. Carbon deposits throughout combustion and exhaust spaces. FTC Decarbonizer’s effect extends through the combustion chamber, exhaust valves and ports, and even turbochargers — depleting carbon build-up and preventing further formation.
  3. Piston ring sticking. Poor combustion, combined with some blow-by of SVO into the crankcase oil, progressively causes sludging, thickening and even gelling of the lube oil. It develops over time, and the best way to keep it at bay is Flushing Oil Concentrate — its purpose-designed detergents remove sludge and dissolve carbon to free up sticking piston rings. Keep a close eye on your oil and do regular oil changes.
  4. Lubrication problems. Thickening and gelling of the oil from vegetable-oil contamination doesn’t bode well for good lubrication. Use Flushing Oil Concentrate at every oil change to avoid oil starvation from blocked or constricted oil passages.
  5. Fungal and bacterial growth (“fuel bug”). SVO is a good nutrient source for fungal and bacterial infestations, which cause filter blockages and damage to fuel injection equipment. FTC Decarbonizer is also formulated as a powerful, effective biocide, which solves this nicely.

FTC Decarbonizer, used to burn straight vegetable oil cleanly in diesel engines

Real Customer Results

50-foot boat, Volvo diesel — Trevor

Trevor runs his Volvo diesel on straight vegetable oil, and built his own system to make biodiesel from waste veg oil too. He runs on biodiesel at start-up and before shutdown; the waste SVO runs through a cheap oil filter heated in an engine-coolant bath to reduce viscosity, and once the engine and SVO reach a stable temperature he switches over to SVO.

Trevor has now run 30,000L of waste SVO (treated with FTC Decarbonizer) through the Volvo, and quickly found FTC is essential for clean burning. His Volvo has recently started to show blow-by, smoke and compression loss from piston sticking — so on our advice he’s about to clear those deposits with Flushing Oil Concentrate. Provided no serious damage has occurred, the old Volvo should burst back into its former glory.

Result: 30,000L of waste veg oil burned cleanly with FTC

Flushing Oil Concentrate, used to control sludge when running vegetable oil

Toyota LandCruiser 60 Series wagon, 2H diesel — Vic

An old girl but a good honest worker, the 2H is a solid, low-stressed engine — and with its pre-combustion technology and inline fuel pump, a good candidate for SVO. Vic built the system himself: the SVO tank sits on a swing-away carrier on the rear, and the exhaust tailpipe lines up with the SVO pre-heat tubing that runs through the holding tank. The pre-heated SVO runs through a Ryco Z9 oil filter to remove debris. The 2H starts and stops on diesel but runs on waste SVO for the bulk of its operation.

Vic’s been running this setup for a few years and credits FTC Decarbonizer with much of his success — it just doesn’t burn clean enough without it.

Result: years of reliable SVO running on an old 2H

For more, see how FTC Decarbonizer works, how it treats diesel fuel bug, and why you should flush a diesel engine.

Running vegetable oil in your diesel? Give the team at Cost Effective Maintenance a call on 07 3376 6188 for advice.

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