Practical steps to reduce fuel consumption in older petrol cars without expensive upgrades

I’m often asked by readers with older petrol cars how to squeeze more miles out of a tank without spending on costly engine work or electrification. Over the years, between my garage experiments and coordinating repairs, I’ve found a set of simple, practical steps that make a real difference — not miracles, but sensible improvements you can do yourself or get done cheaply. Below I share what I do, what I’ve seen work on a range of small petrol engines, and the tweaks that give the best return on effort and money.

Start with the basics: regular maintenance that pays back

Before you chase gadgets, make sure the car’s routine items are in order. A neglected service is the most common reason older cars drink more fuel than they should.

• Fresh spark plugs and leads: Old, fouled plugs cause misfires and incomplete combustion. On many older petrol engines, replacing plugs (I use NGK or Bosch) drops fuel use noticeably and restores throttle response.
• Correct air filter: A clogged air filter chokes the engine and richens the mixture. Replacing it is cheap and often takes 10–15 minutes.
• Quality engine oil at the right viscosity: Heavier or dirty oil increases friction. I run manufacturer-recommended grades — for older petrol engines, a modern semi-synthetic like Castrol GTX or Mobil 1 can help reduce parasitic losses.
• Timely fuel filter replacement: If your car has an inline fuel filter, changing it ensures steady flow and consistent atomisation from the injectors or carburettor.
• Correct tyre pressure: Underinflated tyres increase rolling resistance. I check pressures monthly and before long trips. Follow the door sticker or manual pressures; I add +0.2 bar on long motorway drives for efficiency if the load is light.

Keep the engine breathing and burning clean

Older petrol engines depend heavily on clean airflow and precise ignition. Small gains here translate into lower consumption.

• Mass Air Flow (MAF) and MAP sensors: If your car has them, keeping these sensors clean (with an electronics-safe cleaner) restores correct fueling. Dirty sensors can make the ECU over-fuel the engine.
• Throttle body and idle control cleaning: Carbon build-up causes poor idling and inefficient throttle response. A quick clean can improve drivability and reduce wasted fuel at low speeds.
• Carburettor tuning or injector service: For carb cars, a basic tune and float adjustment matters. For EFI cars, periodically use a reputable injector cleaner additive (I’ve used Wynn’s and Liqui Moly with good results) or have injectors professionally cleaned if spray patterns are poor.

Transmission and driveability

How power gets to the wheels affects fuel use.

• Correct gear use: On manual cars, change up earlier rather than revving high — but not lugging the engine. I aim to keep revs in the flat-ish torque band for older petrols (often 2,000–3,000 rpm depending on the car).
• Clutch and gearbox health: Slipping clutches or worn synchronisers make you use more fuel. If you notice slipping or grinding, address it — the economy gains are worth the repair in the medium term.
• Use cruise control where appropriate: On steady motorway runs, cruise control keeps speed consistent and typically reduces fuel vs variable human throttle inputs.

Reduce weight and drag — small changes, measurable results

I’m old-school on this point: whatever you can remove from the car that you don’t need, remove it.

• Clear out heavy items: Roof boxes, spare tools you don’t use, stacked luggage — they add weight and worsen aerodynamics. I once shaved 30 kg from a weekend-project car and saw a modest but definite improvement on the trip computer.
• Remove roof racks when not in use: Even empty roof rails or racks increase drag significantly.
• Lightweight replacements for obvious items: If the boot is full of heavy, redundant stuff, move it out. I avoid aftermarket “lightweight” upgrades for little-used cars because the cost rarely justifies the gain, but sensible decluttering is free.

Driving technique: the biggest gains for no cost

How you drive is the single most important factor. I coach readers all the time: gentler inputs save fuel.

• Anticipate and glide: Look ahead, ease off the throttle early, coast in gear rather than brake hard. Smooth driving reduces unnecessary acceleration cycles.
• Avoid short trips where possible: Cold engines burn more fuel. Combine errands into one trip so the engine reaches operating temperature and stays there.
• Use higher gears early in manuals and avoid excessive revving: Shift up promptly while maintaining reasonable acceleration.
• Limit air conditioning use at low speeds: AC increases engine load. At higher speeds, AC can be more efficient than open windows due to aerodynamic drag; I switch depending on conditions.

Fuel and additives — sensible choices

You don’t need exotic fuels or expensive “miracle” additives. Stick to known-quality petrol and use additives sparingly and correctly.

• Use reputable fuel brands: Shell, BP, Total, or regional quality suppliers typically have good detergency. I avoid no-name pumps when possible.
• Fuel system cleaner every few thousand miles: A dose of a trusted cleaner (e.g., Liqui Moly or Techron) can help keep injectors and intake valves cleaner and restore economy progressively.
• Don’t mix octane beyond manufacturer recommendations: Higher octane fuel rarely improves economy unless the engine was designed for it or the ECU retards timing for lower octane.

When to consider modest investments

Some low-cost parts bring reliable returns without “expensive upgrades.” I’ll recommend these when the car is sound otherwise.

• High-quality tyres with low rolling resistance: A mid-range Michelin Energy or Continental EcoContact tyre can reduce fuel use and improve safety; expect modest gains and better life.
• Wheel alignment and balancing: Poor alignment increases tyre drag and wear; a simple alignment shop visit often pays back quickly.
• Replace old oxygen sensors: A failing O2 sensor can force an overly rich mixture. Bosch sensors are a dependable choice and usually cheaper than broader engine repairs.

Simple checks and a maintenance checklist

Here’s a compact checklist I run through every few months on my older petrol cars.

These steps won’t turn an older petrol car into a modern hybrid, but combined they add up. What I like about this approach is it focuses on reliability, safety, and real-world fuel savings without needing expensive tuning or aftermarket electronics. If you want, tell me your car model and typical driving conditions and I’ll suggest which items on this list to prioritise first.