The amount added matters, but so does whether the ignition or engine has been used. There is no single amount that we can declare safe for every diesel engine over a website. Give us the vehicle details and the sequence of events so the technician can assess the actual situation.
Why petrol in diesel needs attention
Diesel fuel helps lubricate parts of a diesel injection system. Petrol changes the properties of that fuel, and running the mixture can put fuel-system components at risk. Modern injection equipment can be sensitive, so continuing to drive is not a reliable way to find out whether the vehicle will tolerate it.
The fact that the tank already contained diesel does not make the incident harmless. Do not rely on a percentage suggested online or add more diesel to try to dilute the petrol. The appropriate response depends on the vehicle and what has happened since refuelling.
Caught the mistake while filling?
Stop filling, leave the ignition off and tell the forecourt staff. Keep the receipt or note the pump and product used. Record the approximate litres of petrol added and how much diesel was in the tank beforehand, without switching the ignition on just to check the gauge.
When you arrange assistance, explain if the keys were turned or a start button was used, even briefly. A vehicle that has stayed off and a vehicle that has moved from the pump may require different attention. The technician will explain the proposed work before it starts.
Petrol in diesel after driving
A vehicle may lose power, run unevenly, show a warning or stop after misfuelling. These symptoms are not a measurement of damage. If the engine has run, give the approximate distance, whether it stopped by itself and any attempts made to restart it.
The assessment may need to consider more than the tank. Contaminated fuel may have reached lines, filters or injection components. A fuel drain cannot guarantee that a component has not been affected; further checks or workshop work may be needed depending on the findings.
Cars, vans and commercial diesel vehicles
A small diesel car and a large commercial vehicle may have very different tank arrangements and volumes. Tell us if the vehicle has more than one tank, is carrying a load, belongs to a fleet or has restrictions on where it can be worked on.
For a mobile callout, the location must be safe and accessible. Forecourt rules, height barriers, private-land permissions and remote travel can all affect attendance. Ask about availability and the cost for your own vehicle rather than assuming a standard car price applies to every diesel engine.
Attendance, access and the cost of the work
The quoted cost depends on the vehicle, quantity, access and whether contaminated fuel has circulated. Ask what the proposed work includes and whether further diagnosis or repair may be recommended.
We cover mainland Scotland and the islands. Arrival estimates are confirmed for the vehicle’s actual location and current availability. Time on site is a separate matter and depends on the work. Neither a coverage page nor an initial enquiry is a promise of a fixed completion time.
Before attendance, identify the person authorised to approve the work. The technician explains the proposed service and confirms the cost before starting. If you intend to use a policy, lease agreement or hire-company process, check its requirements with the provider.
Find your coverage areaPetrol in diesel: common questions
Is a small amount of petrol in diesel safe?
We cannot confirm a safe amount for every engine. Stop filling, keep the engine off and obtain advice for the vehicle and amount involved. Do not top up as a substitute for assessment.
Will the fuel filter remove the petrol?
A fuel filter is not a way to separate a petrol-and-diesel mixture. The mixture needs to be assessed and removed as appropriate rather than driven through the system.
Does the engine need replacing?
Not every incident leads to engine replacement. Equally, a website cannot rule out damage. Whether it ran, the contamination and the technician’s findings determine what further work is needed.
Can you attend a van or HGV?
Tell us the vehicle type, tank quantity and location. Commercial vehicles are assessed and quoted for their own requirements; use our van or HGV service information when arranging assistance.