Voted Best Answer
May 05, 2025 - 07:25 PM
Hey there, Bill!
You're asking two very important and valid questions — both about repairing your current oil-burning issue and the broader issue of Kia’s continued use of the Theta II engine despite its known problems. Let’s break both down:
1) Do I have to tear the engine down to replace piston rings?
Yes, replacing piston rings requires a full engine teardown. Here's why:
a) The piston rings sit around the pistons inside the engine cylinders.
b) To access them, the engine must be disassembled, including removing the cylinder head, oil pan, pistons, and often the crankshaft.
c) While piston soak treatments (like Marvel Mystery Oil, Seafoam, etc.) can sometimes temporarily reduce oil consumption caused by carboned-up oil rings, they do not fix worn, cracked, or broken rings or cylinder wall scoring.
So, if your engine continues to burn oil after multiple soak treatments, the only real fix is an engine rebuild or replacement, especially if the oil control rings are stuck or worn out beyond help. Only mechanical replacement will fix the issue in the long term.
2) Why did Kia continue using the Theta II engine after the class-action lawsuit?
Great question — and frustrating for many owners.
The original class-action lawsuits and recalls focused on manufacturing defects, like metal debris from improper machining or bearing wear that caused catastrophic engine failure (mostly due to oil starvation, not oil burning). The class action and recalls addressed specific years and batches, but not all engines were included, possibly because Kia and Hyundai made incremental design or manufacturing changes they believed would resolve the issues. Kia and Hyundai applied “fixes” like software updates (KSDS knock sensors) and adjusted manufacturing processes. But they continued to use the Theta II design in newer cars, including your 2018, with minimal fundamental changes, despite its inherent oil consumption issues.
Why did they keep using it?
1) Cost: Redesigning or retooling an entirely new engine takes years and hundreds of millions of dollars.
2) Short-term fixes like redesigned oil rings, tighter tolerances, and ECU updates were cheaper.
3) Most buyers trade cars before 100k miles, so oil burning at 110k+ wasn’t seen as a warranty liability.
4) Legal settlements don’t always mandate a full recall or redesign — they can require extended warranties or reimbursements only under specific failure types.
5) Unfortunately, many 2016+ Theta II engines (including your 2018) have oil-burning issues that aren't always covered under extended warranties, unless a failure meets exact criteria.
Complaints about oil burning and failures have persisted in later models, and Kia has issued new recalls as recently as 2025 for piston ring defects in other vehicles. The continued use of the Theta II engine, despite its problematic history, likely reflects a mix of corporate decisions, regulatory limits on recall scope, and ongoing attempts to address the defect without a complete redesign.
What You Can Do:
*Check for warranty extensions — some 2018 models may qualify for free repairs if oil consumption exceeds Kia’s threshold (usually 1 quart/1,000 miles).
*Push for a dealer engine replacement — if you have records of oil changes and consumption tests, Kia may cover a short block or full replacement.
* Consider a trade-in — if denied warranty help, these engines often fail catastrophically (rod knock, seized bearings).
Bottom Line:
Piston soaks are a Band-Aid; a proper fix needs mechanical work. Kia continued selling Theta II engines because it prioritized cost savings over reliability, betting on partial fixes and warranty extensions to manage fallout. If you’re out of warranty, your options are limited, but pushing hard with Kia Consumer Affairs or legal help sometimes works.
We at CarParts.com know how frustrating and disheartening this situation can be, especially when it feels like you're doing everything right and still facing the same issues. You're not alone in this, and your concerns are valid. If it comes to rebuilding or replacing the engine, you're making an informed choice based on what's best for long-term reliability. Keep documenting everything, and don't hesitate to push for answers or support where it's due. Wishing you the best moving forward — and if you ever need more help or clarity, we're here for you.
You're asking two very important and valid questions — both about repairing your current oil-burning issue and the broader issue of Kia’s continued use of the Theta II engine despite its known problems. Let’s break both down:
1) Do I have to tear the engine down to replace piston rings?
Yes, replacing piston rings requires a full engine teardown. Here's why:
a) The piston rings sit around the pistons inside the engine cylinders.
b) To access them, the engine must be disassembled, including removing the cylinder head, oil pan, pistons, and often the crankshaft.
c) While piston soak treatments (like Marvel Mystery Oil, Seafoam, etc.) can sometimes temporarily reduce oil consumption caused by carboned-up oil rings, they do not fix worn, cracked, or broken rings or cylinder wall scoring.
So, if your engine continues to burn oil after multiple soak treatments, the only real fix is an engine rebuild or replacement, especially if the oil control rings are stuck or worn out beyond help. Only mechanical replacement will fix the issue in the long term.
2) Why did Kia continue using the Theta II engine after the class-action lawsuit?
Great question — and frustrating for many owners.
The original class-action lawsuits and recalls focused on manufacturing defects, like metal debris from improper machining or bearing wear that caused catastrophic engine failure (mostly due to oil starvation, not oil burning). The class action and recalls addressed specific years and batches, but not all engines were included, possibly because Kia and Hyundai made incremental design or manufacturing changes they believed would resolve the issues. Kia and Hyundai applied “fixes” like software updates (KSDS knock sensors) and adjusted manufacturing processes. But they continued to use the Theta II design in newer cars, including your 2018, with minimal fundamental changes, despite its inherent oil consumption issues.
Why did they keep using it?
1) Cost: Redesigning or retooling an entirely new engine takes years and hundreds of millions of dollars.
2) Short-term fixes like redesigned oil rings, tighter tolerances, and ECU updates were cheaper.
3) Most buyers trade cars before 100k miles, so oil burning at 110k+ wasn’t seen as a warranty liability.
4) Legal settlements don’t always mandate a full recall or redesign — they can require extended warranties or reimbursements only under specific failure types.
5) Unfortunately, many 2016+ Theta II engines (including your 2018) have oil-burning issues that aren't always covered under extended warranties, unless a failure meets exact criteria.
Complaints about oil burning and failures have persisted in later models, and Kia has issued new recalls as recently as 2025 for piston ring defects in other vehicles. The continued use of the Theta II engine, despite its problematic history, likely reflects a mix of corporate decisions, regulatory limits on recall scope, and ongoing attempts to address the defect without a complete redesign.
What You Can Do:
*Check for warranty extensions — some 2018 models may qualify for free repairs if oil consumption exceeds Kia’s threshold (usually 1 quart/1,000 miles).
*Push for a dealer engine replacement — if you have records of oil changes and consumption tests, Kia may cover a short block or full replacement.
* Consider a trade-in — if denied warranty help, these engines often fail catastrophically (rod knock, seized bearings).
Bottom Line:
Piston soaks are a Band-Aid; a proper fix needs mechanical work. Kia continued selling Theta II engines because it prioritized cost savings over reliability, betting on partial fixes and warranty extensions to manage fallout. If you’re out of warranty, your options are limited, but pushing hard with Kia Consumer Affairs or legal help sometimes works.
We at CarParts.com know how frustrating and disheartening this situation can be, especially when it feels like you're doing everything right and still facing the same issues. You're not alone in this, and your concerns are valid. If it comes to rebuilding or replacing the engine, you're making an informed choice based on what's best for long-term reliability. Keep documenting everything, and don't hesitate to push for answers or support where it's due. Wishing you the best moving forward — and if you ever need more help or clarity, we're here for you.
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