It is important to have the well suited fully synthetic 15w40 oil. Let’s take you step by step, type by type, and find the best fully synthetic 15w40 oil for you.

Our review process: Show/Hide

Our Top Picks:

Best Overall: Buy: Shell Rotella Diesel Engine Oil READ REVIEW

Best For Outstanding Protection: Buy: Royal Purple Fully Synthetic 15W40 Oil READ REVIEW

Best For Better Price: Buy: Shell Rotella Fully Synthetic 15W40 Oil READ REVIEW

Best For Gasoline Engine: Buy: Chevron Fully Synthetic 15W40 Oil READ REVIEW

Best For Engine Noise: Buy: Lucas Oil Fully Synthetic 15W40 Oil READ REVIEW

Best With Zinc: Buy: Triax Fully Synthetic 15W40 Oil READ REVIEW

Best For Long Life: Buy: Sinopec Fully Synthetic 15W40 Oil READ REVIEW

Best Overall: Shell Rotella Diesel Engine Oil

Buy on Amazon

If you often find yourself scrambling for good oil, Shell Rotella Diesel Engine Oil is your solution. The shell rotella diesel engine oil is made with great stuff and it is worth the money. 30 diesel engine oil with triple protection plus technology uses synthetic base oils plus advanced additive technology to provide protection against wear, deposits and oil breakdown. This synthetic blend oil provides excellent equipment protection, long engine life and maintains viscosity control under high temperatures.

The oil comes with the best deal, It allows for excellent protection and has a unique design. Also, the oil is used for best value, has excellent wear protection and it is good enough. Most importantly, the shell rotella diesel engine oil maintains oil viscosity over the recommended drain interval.

Almost all customers quickly discovered that the oil is good for cars or motorcycles. And, they say that the oil protects against wear, deposits, and oil breakdown. Moreover, they strongly agree that oil has t6 at 15w40 as well. Overall, for almost all customers, Shell Rotella product was what they were looking for.

• This is technical, has improved oxidation and it is made for gas engines.
• Case of three 1-gallon bottles with an ergonomic design for easy handling and pouring.
• Improves low-temperature flow (compared to conventional 15w-40 oils).
• This provides excellent piston cleanliness, exceeding Mercedes and volvo limits.

Best For Outstanding Protection: Royal Purple Fully Synthetic 15W40 Oil

Buy on Amazon

Next on the list, we've got yet another oil that manages to win our hearts. It's the Royal Purple Fully Synthetic 15W40 Oil and it's widely considered as one of the most convenient oils you can buy. The royal purple fully synthetic 15w40 oil is used to lubricate, clean, and cool engines with the utmost efficiency. Make sure this fits by entering your model number. Moreover, the oil is commercial and it has bearing corrosion.

The oil is suitable for outstanding protection and it allows for better fuel mileage. Further, it provides longer oil life and also offers unsurpassed protection in a full oem. Most importantly, the royal purple fully synthetic 15w40 oil is compatible with mineral or other synthetic oils.

Most buyers found that the oil is even more quiet and smooth with the royal purple. And, a few say that oil is the perfect solution. Picture this, no wear on your bearings, repeat no wear on your bearings. In short, at the price, they believe that they got a steal of a deal with it.

• Meets ilsac gf-5 and dexos1 performance requirements.
• This has increased fuel efficiency and it works well.
• Better protection of the expensive catalytic emission system.
• This has additives for diesel but mobil 1 makes 15w-40 full synthetic.

Best For Better Price: Shell Rotella Fully Synthetic 15W40 Oil

Buy on Amazon

We know from years of feedback from readers, amazon sellers, and family and friends what most people want in a convenient and appropriate oil. The Shell Rotella Fully Synthetic 15W40 Oil is exactly that - it's a simple oil that hits all the right notes. The shell rotella fully synthetic 15w40 oil provides better low temperature flow and increased fuel economy performance, without compromising durability, compared to conventional sae 15w. Increased shear stability for better viscosity control and optimal engine oil pressure. And, the oil lasts longer, is smoother and it runs great.

The oil is designed for easy handling and pouring. And, it runs smoother, can be trusted for good quality and it is made for good stuff. Finally, the shell rotella fully synthetic15w40 oil is good for corrosion protection and it is compatible with conventional oils.

Most buyers agree that oil is everywhere else being rural here. In addition, they say that the oil is designed for diesel engines but it works great in older vehicles with high mileage. Further, a few strongly agree that the oil is not 100% synthetic like amsoil. In short, at the price, they believe that they got a steal of a deal with it.

• You need your hard-working engines to keep up with your demanding workload.
• This also produces more soot and improves low-temperature flow.
• This has more power and higher torque but with higher compression ratios.
• Conventional oils form sludge deposits over time, reducing your engine's efficiency and lifespan.

Best For Gasoline Engine: Chevron Fully Synthetic 15W40 Oil

Buy on Amazon

The Chevron fully synthetic 15w40 oil is capable of outshining several other oils featured in this list in overall features for the price point. The Chevron fullysynthetic 15w40oil is common and it works for gas engines. 40 with isosyn advanced technology is a super-premium quality conventional engine oil which exceeds industry and engine manufacturers’ performance requirements. And, this is made worth the price and it is smoother.

Lastly, the Chevron Fully Synthetic 15W40 Oil is suitable for outstanding protection, is made for good stuff and it is great for lawn mowers.

Almost all buyers quickly discovered that the oil does not meet the same spec requirements. Further, they strongly agree that the oil can be used in a gasoline engine, but it is formulated for diesel engines. And, they strongly agree that this oil is approved for gasoline vehicles, calling for an api of 15w40 motor oil. Overall, the tone of buyers is very positive and we believe that oil suits the purpose.

• It is priced right and it is robust.
• These make for a great buy, work well and it does the job.
• Payment for chevron lubricant-related damage to your equipment, including parts and labor.
• Premium quality heavy duty motor oil manufactured in the USA.

Best For Engine Noise: Lucas Oil Fully Synthetic 15W40 Oil

Buy on Amazon

The Lucas Oil Fully Synthetic 15W40 Oil's material feels more premium than its price would suggest. The lucas oil fully synthetic 15w40 oil is worth the money and it is highly recommend. Always check your vehicle's owner's manual to verify that this is the correct weight of motor oil for your vehicle. Further, this is best for fast service and it is safe.

Most importantly, lucas oil, fully synthetic15w40 oil, is made from crude oil and is used to lubricate, clean, and cool engines.

Most customers quickly discovered that the oil can be used at the correct percentage. Further, they strongly agree that oil is a great price for this great lucas oil. Moreover, a few also found that this oil has performed well so far.

• This is made for older engines and it is good for very high quality.
• This can often cost more than conventional motor oil.
• This oil is one of the better oils and is recommended for generac engines.
• This could have been used by Lucas. is what makes the difference.

Best With Zinc: Triax Fully Synthetic 15W40 Oil

Buy on Amazon

The Triax Fully Synthetic 15W40 Oil's high-end materials makes sure that it ages well with use. The triax fullysynthetic 15w40 oil allows dry lubrication, extreme cold rapid starts, significantly reduced wear, improved fuel economy, and an outrageously long fluid life. The manufacturer says: Our high end synthetic hydraulic oils are capable of delivering 15, 000 hours of fluid life. In addition, it is brand new, is smoother and it is safe.

The oil offers superior performance parameters, durability, and unrivaled fuel economy. Most importantly, the triax fully synthetic 15w40oil is good for oil changes and maintenance are essential but costly parts of equipment ownership.

Most customers opine that the oil is superior to almost everything out there, at much more reasonable prices. Also, they strongly agree that oil is much better than any other in the market. In addition, they strongly agree that this is a top quality synthetic oil developed with diesel engines in mind.

• Manufacturer says: in 2015, we made our fluids available to the general consumer market.
• This is noticed change to a synthetic blend grade oil.
• It has state-of-the-art dispersal and ash control systems to keep your engine extremely clean.
• This has considerable fuel efficiency benefits and a very long life even in marine environments.

Best For Long Life: Sinopec Fully Synthetic 15W40 Oil

Buy on Amazon

The Sinopec fully synthetic 15w40 oil is the most reliable oil on the market today. The Sinopec Fully Synthetic 15W40 Oil is running strong and it is perfect for free delivery. Sinopec diesel engine oil tulux t700 full synthetic ck-4 is formulated using synthetic high viscosity index group 3 base oils and superior low saps additive packages. In addition, it is commercial and it is strong.

Lastly, the sinopec fully synthetic 15w40 oil include, but is not limited to wy, wa, MT and parts of id, nd, sd, ne, nm, mo, co, tx & ks.

To sum up, the tone of buyers is very positive and we believe that oil suits the purpose.

• Pack size: 55 gallon drum (200l volume).
• This is good for rural locations and it is made for good stuff.
• This is designed to meet euro v and euro vi exhaust emissions standards.