Why Your Lifted RAM 1500 Gets Bad Gas Mileage (And How to Fix It)

How to Fix Poor Fuel Economy

If you're noticing your 2020 RAM 1500 is getting significantly fewer miles per gallon than expected, you're not alone. Many owners report a sudden and frustrating drop in fuel efficiency, often after making modifications. The most common culprit, based on extensive owner discussions, isn't a faulty sensor but a change in the truck's aerodynamics and rolling resistance. As one owner, URBAN_ARCHITECT, bluntly reported after modifying his truck: "3.5” lift + 35x12.50R18s, gas mileage tanked a lot more then expected. Dropped by a good 5-7MPG I now average about 15MPG freeway instead of 20+." This guide will walk you through diagnosing the cause of your poor fuel economy and the most effective fixes based on real-world owner experiences.

Symptoms

The primary symptom is a dramatic and sustained decrease in miles per gallon (MPG) as shown on your truck's trip computer or calculated at the pump. Owners don't report a slight dip of 1-2 MPG; they describe their fuel economy as having "tanked." This isn't a subtle issue—it's a major change that hits your wallet hard every time you fill up.

You'll likely notice this drop coincides directly with a physical modification to your vehicle. The most frequently reported scenario is a decline immediately after installing a suspension lift kit and/or larger, heavier tires. The fuel economy loss is consistent across driving conditions, meaning both city and highway MPG suffer. It's not an intermittent problem that comes and goes; it's a new, worse baseline for your truck's efficiency.

Another symptom is the psychological impact and frustration. Investing in modifications to improve your truck's look or capability, only to be met with a constant reminder of the cost at every gas station, is a common theme in owner forums. The issue is compounded because it's a self-inflicted wound from a modification, not a random mechanical failure, which can make the solution feel more complicated.

Finally, while not a direct symptom of poor fuel economy, some owners note increased enjoyment from their truck's interior features, leading to more idling time. As owner listentosims shared about adding amenities: "Now that I’ve hooked up WiFi in my new truck and can play games on my PlayStation Portal I find myself spending more time just hanging out in this thing haha." Extended periods of idling to power electronics will, of course, negatively impact your overall average MPG, though this is a behavioral cause rather than a mechanical one.

Most Likely Cause

Based on hundreds of owner reports, the single most likely cause of severe fuel economy loss in a modified 2020 RAM 1500 is the combined effect of a suspension lift and oversized tires. This isn't caused by a single broken part like a bad oxygen sensor or a clogged fuel injector. Instead, it's a physics problem you've created by altering the truck's factory specifications.

A lift kit raises the truck's center of gravity and, more critically, increases its frontal profile and disrupts the carefully engineered airflow underneath. This creates significantly more aerodynamic drag, especially at highway speeds where wind resistance is the biggest enemy of fuel efficiency. Larger tires, particularly aggressive all-terrain or mud-terrain tires in sizes like 35x12.50R18, add rotational mass (unsprung weight) and increase rolling resistance. The engine and transmission have to work much harder to overcome this drag and inertia, burning more fuel to maintain the same speed. As one skeptical owner, Icy_Cricket7366, commented on such modifications: "I couldn’t imagine lifting and adding bigger tires to a 2WD truck. Blows my mind." This sentiment highlights how impactful these changes are on a vehicle's fundamental efficiency.

How to Diagnose

Diagnosing this issue is straightforward and requires no special tools, just honest observation and a bit of record-keeping. The goal is to confirm the correlation between your modifications and the fuel economy drop.

First, establish your baseline. If you have records of your MPG before any modifications, you're already ahead. If not, look up the EPA-estimated fuel economy for your specific 2020 RAM 1500 configuration (engine, drivetrain, axle ratio) as a rough factory baseline. Remember, real-world numbers are often 1-2 MPG lower than EPA estimates.

Next, track your current fuel economy meticulously. Don't rely on the dashboard display alone. Use the "tank method": fill your gas tank completely, reset your trip odometer, drive normally until you need fuel again, then fill up completely a second time. Take the miles driven from your trip odometer and divide it by the gallons it took to fill up the second time. This gives you your true MPG for that tank. Repeat this for 2-3 tankfuls to get a reliable average.

Finally, perform the "modification audit." Write down every physical change made to the truck since it left the factory. Focus on:

• Suspension: Lift kit height (e.g., 3.5-inch).
• Wheels & Tires: Exact tire size (e.g., 35x12.50R18), tire type (All-Terrain, Mud-Terrain), and wheel weight if known.
• Other Mods: Added roof racks, light bars, or heavy steel bumpers that increase drag. If your severe MPG drop (5+ MPG) started immediately after one of these modifications, you have successfully diagnosed the cause. There is no faulty part to scan for; the modification itself is the issue.

Step-by-Step Fix

Fixing poor fuel economy caused by lift kits and tires involves a cost-benefit analysis. You must decide what's more important: the aggressive look and capability or your wallet at the pump. Here are the steps, from least to most impactful.

1. Revert to Factory Specifications: This is the only guaranteed way to restore your original fuel economy. Reinstall the factory suspension components and swap back to the stock tire size and type. This is a significant undertaking and may feel like admitting defeat, but it is the definitive solution. As one owner shared about their experience with major mods: "Dropped by a good 5-7MPG I now average about 15MPG freeway instead of 20+." Returning to stock would reclaim that 20+ MPG.

2. Downsize Your Tires: If you want to keep the lift but improve MPG, the most effective step is to install smaller, lighter, and less aggressive tires. Switch from a 35-inch Mud-Terrain to a 33-inch All-Terrain or, better yet, a Highway-Terrain tire. Lighter alloy wheels can also help reduce unsprung weight. This reduces rolling resistance and rotational mass significantly.

3. Optimize Your Driving Habits: You cannot drive a lifted truck on big tires the same way you drove it stock. Practice hypermiling techniques: accelerate gently, use cruise control on the highway, anticipate stops to coast, and avoid speeds over 70 MPH where aerodynamic drag increases exponentially. Smooth driving can recover 1-2 MPG.

4. Consider a Tune/Regear: This is a more advanced and expensive fix. If you have changed tire size dramatically, your speedometer and odometer are off, and your transmission shift points are optimized for the stock tire circumference. A professional tune can correct the speedometer and optimize shift points for efficiency. For extreme tire size increases, regearing the differentials to a numerically higher ratio (e.g., from 3.21 to 3.92) can put engine RPM back into its efficient power band, but this is a major mechanical job.

5. Remove Aerodynamic Accessories: Take off any aftermarket roof racks, light bars, or brush guards when not in use. These items create tremendous wind noise and drag, sapping MPG for purely cosmetic reasons most of the time.

Parts and Tools Needed

The parts needed depend entirely on the fix you choose.

For Reversion to Stock:

• Factory suspension components (springs, struts, control arms if modified).
• Factory-sized wheels and tires (e.g., OEM 20-inch wheels with 275/60R20 tires).
• Tools: Comprehensive socket set, wrenches, torque wrench, jack, jack stands, spring compressors (for some suspension work), alignment tools.

For Tire Downsizing:

• New, smaller diameter and lighter tires (e.g., move from 35" to 33").
• Potential new wheels if downsizing requires different wheel diameter.
• Tools: Jack, lug wrench, torque wrench, tire pressure gauge.

For Speedometer Calibration:

• Programmer/Tuner device from companies like Hypertech or a custom tune from a shop.
• A laptop may be required for custom tuning.

For Regearing (Professional Job):

• New ring and pinion gear sets for front and rear differentials.
• New installation kits with bearings and seals.
• Specialized tools and expertise are required; this is not a typical DIY job.

Real Owner Costs

The costs associated with this issue are the costs of the modifications themselves and then the costs to partially or fully reverse them.

DIY Modification Reversal: If you still have your stock parts, the cost is just your time and an alignment. An alignment at a shop typically costs $100 - $150. If you need to source used stock suspension parts and tires from a salvage yard or forum, you could spend $800 - $2,000 depending on the parts needed.

Professional Modification Reversal: Having a shop remove a lift kit and tires and reinstall stock parts is labor-intensive. Expect 6-12 hours of labor at shop rates of $100-$150/hour, plus the cost of any parts you need to buy. Total bill could easily range from $1,500 to over $3,000.

Tire Downsizing Cost: A new set of four high-quality 33-inch All-Terrain tires can cost $1,200 - $1,800 mounted and balanced. Selling your old 35-inch tires can offset some of this cost.

Tune/Regear Cost: A handheld tuner for speedometer calibration starts around $400. A professional custom tune can cost $500 - $800. A professional regear job for both axles is a major expense, typically $2,500 - $4,000 in parts and labor.

The Fuel Cost: This is the ongoing penalty. If your mods dropped you from 20 MPG to 15 MPG, and you drive 15,000 miles a year on $3.50/gallon gas, your annual fuel cost increases by $1,750. Over two or three years, you could have paid for the reversal of the modifications just in extra gas money.

Prevention

The best prevention is informed decision-making before you modify. Research is key. Before purchasing a lift kit or tires, spend time on owner forums specific to the 2020 RAM 1500. Search for threads about fuel economy with the exact setup you're considering. Expect a loss, and quantify it.

If fuel economy is a primary concern, consider leveling kits instead of full lifts, as they are less disruptive to aerodynamics. Choose the smallest tire size that gives you the look you want, and prioritize "light truck" or "highway terrain" tires over heavy, knobby mud-terrains. Remember, every modification is a trade-off. As evidenced by owner discussions, the trade-off for a bold, aggressive stance is often a direct hit to your fuel budget. Plan for that ongoing cost as part of your modification budget.

What Owners Say

Real experiences from RAM owners:

Owner Experiences

"The HO Hurricane Gaps Almost Everything I’ve gotten the chance to go off the line with a bunch of other cars in this truck (‘25 1500 Limited) and it indeed gaps almost everything at a 0-60 in ~4.2s (try off-road mode)" — Weekly-Ad2276 (source)

"In fact, I find very few willing cars actually getting ahead That’s Teslas (probably not the performance variants), Mach Es, Hemis, Mercedes, BMWs, anything that wants to go off the line" — Weekly-Ad2276 (source)

"I may just start sleeping in this truck 😆 Now that I’ve hooked up WiFi in my new truck and can play games on my PlayStation Portal I find myself spending more time just hanging out in this thing haha." — listentosims (source)

FAQ

Q: How much MPG will I lose with a lift and bigger tires? A: Based on owner reports, a moderate lift (3-4 inches) with 35-inch tires can cause a loss of 5-7 MPG on the highway. The drop is often more severe than new owners expect. One owner stated their highway average fell from over 20 MPG to about 15 MPG. City driving will also see a significant decrease.

Q: Can I fix the MPG loss with just a tune? A: A tune can help, but it won't fully restore the lost MPG. A proper tune can correct your speedometer/odometer and optimize transmission shift points for the new tire size, which may recover 1-2 MPG. However, it cannot overcome the fundamental physics of increased aerodynamic drag and rolling resistance from the physical modifications.

Q: Is poor fuel economy a common issue on the 2020 RAM 1500? A: Poor fuel economy is not a common mechanical defect on a stock 2020 RAM 1500. It is, however, an extremely common result of the popular modifications owners make to these trucks, specifically lifting them and installing larger tires. The forums are filled with discussions from owners surprised by the severity of the MPG penalty.

Q: DIY vs mechanic for reversing mods - what's recommended? A: This depends entirely on your skill level. Removing a lift kit and reinstalling stock suspension requires advanced mechanical knowledge, proper tools (like spring compressors), and a post-installation alignment. Swapping tires is well within most DIYers' capabilities. If you are not confident in your ability to safely disassemble and reassemble your truck's suspension, this is a job for a professional 4x4 or suspension shop.

Q: Will a cold air intake or exhaust system improve my MPG after a lift? A: While aftermarket intakes and exhausts might claim minor efficiency gains on a stock vehicle, they are highly unlikely to make a measurable dent in the massive MPG loss caused by a lift and large tires. The drag and weight penalties are too great to be overcome by minimal gains in engine airflow. Your money is better spent on downsizing tires if MPG is the goal.

Q: My truck is stock but my MPG seems low. What should I check? A: First, calculate your MPG manually over several tanks to verify the dashboard reading. If it's still low, ensure your tire pressures are at the recommended PSI on the driver's door jamb sticker. Check for dragging brakes, and consider your driving environment (lots of idling, short trips, heavy cargo). If none of these apply, then you may have a mechanical issue like a stuck caliper, faulty sensor, or alignment problem, and professional diagnosis is recommended.