How Can I Improve Gas Mileage In My Subaru Forester?

By Nick Marchenko, PhD

Updated: September 11, 2023

Why is your Subaru Forester mpg so low? In a world that's rapidly embracing electric and hybrid technology, many remain loyal to their gasoline or diesel-powered Subaru Foresters. This decision stems from the uncomplicated nature and convenience of these engines when compared to their electric or hybrid counterparts.

However, nearly every Subaru Forester owner has, at one point or another, grappled with the need to curtail their vehicle's fuel consumption. Factors like weather conditions and the vehicle's health can significantly influence fuel efficiency.

Optimizing the Subaru Forester's fuel economy can result in increased range, monetary savings, and an overall enhanced driving experience.

This piece will delve into the core reasons behind high fuel consumption and offer tips to enhance your mpg.

Key Takeaways:

• Diesel engines usually consume 20-30% less fuel than gasoline engines, given that diesel is denser and offers better efficiency.
• To attain optimal fuel efficiency in your Subaru Forester, it's prudent to stick to recommended speeds, utilize cruise control, and activate the ECO-Mode when available.
• Keeping your Subaru Forester in peak condition, especially concerning spark plugs, filters, oil, and the entire engine setup, can dramatically reduce unnecessary fuel usage.
• Modern Subaru Foresters, equipped with an array of sensors, can offer precise data on system anomalies that could lead to heightened fuel consumption.

Which Subaru Forester engine offers the best mileage?

Numerous elements influence the fuel efficiency of the Forester, including the engine's design, cylinder count, and valve quantity. While there's a belief that larger engines consume more fuel, that's not always the case.

Engines with smaller capacities (up to 1 liter - 1.2 liters) tend to consume less fuel due to fewer cylinders and reduced fuel burn per stroke. Consequently, their fuel economy is impressively efficient.

On the flip side, engines with larger capacities can also showcase commendable fuel efficiency. A potent engine can effortlessly propel a vehicle, consuming lesser fuel in the process. By strategically placing these engines in lighter vehicles, fuel economy can be notably improved.

Which is more fuel-efficient: diesel or gasoline engines?

The fuel consumption of diesel engines generally falls below their gasoline counterparts, with a difference of around 20-30%.

Additionally, diesel engines boast superior efficiency and towing capacities, making them ideal for transporting heavy loads. They also excel in torque generation, especially at lower RPMs. However, Subaru's gasoline engines tend to be more potent, offer quicker acceleration, and provide smoother dynamics.

The efficiency of diesel engines is inherently tied to the characteristics of diesel fuel. It has enhanced combustion efficiency. Given its dense nature, diesel typically releases about 15% more energy upon combustion than gasoline. This means at idle, diesel engines tend to consume 2-3 times less fuel than gasoline engines. This efficient combustion also results in diesel engines generating less heat during operation, making them more durable and torque-rich.

Thus, when choosing between the two:

• If speed and agility top your list, then a gasoline Subaru Forester should be your pick.
• For those prioritizing fuel efficiency and superior traction, a diesel Subaru Forester might be more up your alley.

Boosting the Fuel Mileage of Your Subaru Forester

Decreasing fuel consumption can be influenced by myriad factors and might yield varying results based on the conditions and model year of your Subaru Forester.

Here, we're laying out some general guidelines. Stick to them and you're bound to see an improvement in your Forester's fuel economy.

Maintain a Steady Speed

If you're the type to floor the accelerator or routinely drive at top speeds, then the increased fuel consumption of your Forester shouldn't come as a shock.

Pushing your engine to its limits means burning more fuel. But, cruising around at 20 miles per hour isn't going to help your cause either.

The sweet spot? Well, each Forester variant has a recommended cruising speed. Abiding by this speed ensures optimal fuel consumption. This speed is typically displayed on your Forester's dashboard, and sometimes even highlighted for convenience.

Engage Cruise Control

For those Foresters equipped with cruise control, make sure to engage it on extended drives. Your Subaru will autonomously regulate the fuel delivered to the cylinders. Consistent throttle responses result in consistent fuel consumption – and that's good for your mpg.

Switch to ECO-Mode

Forester models equipped with an ECO mode should definitely take advantage of it. By activating this mode, the vehicle autonomously optimizes various parameters and deactivates non-essential systems. This results in improved fuel efficiency and reduced emissions.

Smooth Acceleration is Key

Heavy-footed acceleration causes your Subaru Forester to gulp down fuel. Aim for gentle, even pressure on the gas pedal. Think of it this way: imagine there's a cup of your favorite brew on the dash, and your goal is to accelerate without spilling a drop.

Minimize Idle Time

Even at low revs, the Forester consumes its fair share of fuel. For instance, an average vehicle with a 2.5-liter engine might use more than a cup of fuel every 10 minutes of idling. Extended idling? Not a great idea. If you anticipate a long wait, consider shutting off the engine.

Shutting Off in Traffic: Yea or Nay?

A common myth suggests that shutting off the engine at every red light will save you fuel. Here's the truth: The fuel saved is only substantial if you're idling for extended periods (think 30-minute traffic jams). Plus, restarting consumes more fuel than just letting it idle.

Moreover, frequently turning off and restarting the engine can expedite starter wear and tear. So, gauge the situation. If you're facing a short wait, it's probably best to keep the engine running. But if it's going to be a lengthy halt, turning off might be beneficial.

Lighten that Subaru Forester's Load

You know, sometimes, especially on those epic road trips, we need our Forester packed to the brim. But on the daily? Not so much.

Anything you've got in there that's not essential - be it tools, bags, or whatever other knick-knacks - is just dead weight. Lighten that load and watch your fuel efficiency rise.

Keep a Keen Eye on Tire Pressure

It's often overlooked, but those tires? They need to be right on the money. Low pressure means more resistance and, you guessed it, more fuel consumption. Stay on top of it and keep those tires pumped!

Use that AC Sparingly in Your Forester

Now, I'm not saying roast in there. But if your Forester's already cool, give the AC a break now and then. You'll save on fuel and hey, roll down those windows and enjoy the breeze.

Limit the Use of Power Guzzlers

This is for those times when the fuel gauge is making you nervous. Shut off anything drawing power - lights, heaters, all that jazz. But be smart – don't be driving in the dark without headlights.

Keep Your Subaru Forester in Tip-Top Shape

Your Subaru's a machine, and like all machines, it runs best when it's well-maintained.

Spark Plugs

Worn-out spark plugs? Not your friend. They can hinder your engine's performance and, believe it or not, jack up your fuel consumption.

Filters

Filters matter, my friend. A clogged filter can make your engine work harder than it needs to, burning more fuel in the process. Keep 'em clean and fresh.

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Oil

And, of course, that golden liquid – oil. Regularly check and replace it. A well-lubricated engine is a happy engine, and a happy engine sips, not gulps, fuel.

Overall Condition of Engine Components

As the miles roll on, the engine components of your trusty Subaru Forester start showing their age. They've been there for you during those Sunday cruises, as well as during those mad dashes to the grocery store. However, time takes its toll.

As wear sets in, the engine struggles a tad more, gobbling up extra fuel along the way. If you're finding your Subaru's thirst hard to quench, despite giving it the TLC suggested in this article, it might be time to inspect for some deep-seated wear. Here's what to keep an eye out for:

• Cylinder-piston group wear. Challenges like burrs in the cylinders and burned pistons can make your Forester's engine work overtime, consuming more fuel than usual;
• Valve wear. Valves need to maintain their tight seal. When they start letting loose, your Subaru might just guzzle extra fuel without packing more punch. And hey, nobody likes those grinding noises;
• Crankshaft issues. The crankshaft should be steady as a rock. Any side-to-side movement? That's energy lost and more fuel down the hatch.

It's Not All About Quantity: The Mixture Matters

The Subaru Forester, like any champ of the road, thrives on a precise cocktail of fuel and air. Lean or rich – that balance is key.

A rich mixture means your Forester is taking a bigger gulp than needed, evidenced by that choking sound when you hit the gas and the unsightly black smoke trailing behind.

Several culprits could be behind this, from a misbehaving pump, a moody ECU, to pesky injector issues. Time to roll those sleeves up!

Is Your Forester Trying to Tell You Something?

Today's Subaru Foresters are more than just wheels and an engine; they're a tech marvel. So, got any flashy lights on that dashboard? The 'Check Engine' glaring at you, perhaps?

Here's a pro tip: Hook up an OBD-2 appliance. If there are glitches or sensor issues misleading your Forester's ECU, it could be burning more fuel than it really needs.

Consider a Performance Programmer for Your Forester

The modern Forester's got smarts, but with a performance programmer, you can fine-tune those smarts to work just the way you want.

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Connect this little gadget, adjust a few settings via your smartphone, and you could get your Forester to sip, not gulp, even if it means dialing down the power a notch.

Rolling to a Conclusion

So, as we cruise to the end, remember: Whether it's the condition of the engine or just being attentive to your Subaru Forester's needs, there are plenty of routes to maximize fuel efficiency. Keep it in gear, and you're bound to keep those miles rolling smoothly!